Micropyle

“ Leydig) .
[2] nIn the genera Orchestoidea, Orchestia, Allorchestes, Montagua, Batea n.g., Amphilochus, Atylus, Microdeutopus, Leucothoë, Melita, Gammarus (according to Meissner and La Valette) , Amphithoë, Cerapus, Cyrtophium, Corophium, Dulichia, Protella and Caprella.ote
[3] Little as a name may actually affect the facts, we ought certainly to confine the name “micropyle” to canals of the egg-membrane, which serve for the entrance of the semen. ”

“ When the embryo follows the direction of the axis of the seed, it is axile or axial (fig. 43) ; when it is not in the direction of the axis, it becomes abaxile or abaxial. In campylotropal seeds the embryo is curved, and in place of being embedded in endosperm, is frequently external to it, following the concavity of the seed (fig. 44) , and becoming peripherical, with the chalaza situated in the curvature of the embryo, as in Caryophyllaceae.
It has been already stated that the radicle of the embryo is directed to the micropyle, and the cotyledons to the chalaza. ”

“ The ramified filaments, and jointed or coralloid bodies, which the microscope discovers to us on the surface of most vegetable and animal infusions, when they become putrid, and which were supposed by Needham to be zoophytes, were found by Ellis to be of that genus of fungi called mucor, many of which have been [424] figured by Michelius, and described by Linnæus. Their vegetation is so quick, that they may be seen to grow and seed under the eye of the observer. Other instances of similar mistakes in Needham’s experiments may be seen in Ellis’s paper, Philos. ”

“ SECTIONS AND HOW TO CUT THEM, WITH SOME REMARKS ON DISSECTION. Many objects are almost worthless to the microscopist until the extraneous matter is removed from them; and this is frequently difficult in the extreme to perform satisfactorily. As an instance, certain Foraminifera may be mentioned in which the cells are placed one upon another, consequently the object must be reduced to a certain degree of thinness before a single uniform layer of these cells can be obtained to show something of the internal arrangements. ”

“ Many are free-growing, and may be found attached to the stems of water-plants, but they are extremely minute, and will hardly be noticed until the microscopist has acquired considerable experience, nor even then—with such an instrument as we have postulated—will he see more than a tiny pear, with a straight line, the margin of the cup, on each side of its summit. The flagellum will be quite invisible.
Some similar organisms may, nevertheless, be found which, though still minute, are within the range of a properly managed quarter-inch objective. ”

“ In stained preparations it can be shown that the process of microgamete formation is preceded by fragmentation of the nucleus, the chromosomes proceeding to the periphery of the sphere and each becoming surrounded by a portion of protoplasm. The microgamete, therefore, is composed of these two elements drawn out into a thread—a chromatin filament enclosed in a covering of protoplasm. In the granular spheres there is no fragmentation of nucleus or filament formation, the minute nucleus remaining central surrounded by its circle of haemozoin rods. ”

“ It was on the third day of the diatoms that Hapley became aware of a novel addition to the local fauna. He was working late at the microscope, and the only light in the room was the brilliant little lamp with the special form of green shade. Like all experienced microscopists, he kept both eyes open. It is the only way to avoid excessive fatigue. One eye was over the instrument, and bright and distinct before that was the circular field of the microscope, across which a brown diatom was slowly moving. With the other eye Hapley saw, as it were, without seeing. ”

“ I may here add that almost every kind of substance used by the microscopist suffers from careless handling. Many leaves with fine hairs are robbed of half their beauty, or the hairs, perhaps, forced into totally different shapes and groups; many insects lose their scales, which constitute their chief value to the microscopist; even the glass itself distinctly shows the marks of the fingers if left uncleaned. Every object must also be thoroughly dry, otherwise dampness will arise and become condensed in small drops upon the inner surface of the thin glass cover. ”

“ With such powers as those with which we shall have to deal, it will rarely happen that, for example, a bottle of water in which no life is visible will be worth the carrying-home; whilst, on the other hand, a few months’ practice will render it not only possible, but easy, not only to recognise the presence, but to identify the genus, and often even the species, of the forms of life present. Moreover, these low powers, affording a general view of the object, allow the relation to each other of the details revealed by the power of the compound microscope to be much more easily grasped. ”

“ The rate of movement of the granules is accelerated by moderate warmth and retarded by cold. It is in viewing the circulation in water plants that the warm stage of the microscope is brought into use. Borne along with the protoplasmic stream are a number of solid particles consisting of starch granules and other matters. The method of viewing the circulation is by cutting sections off a portion of the plant with a very sharp knife, and arranging them in a growing cell with a few drops of water, and covering over with a thin cover-glass. ”

“ This is largely because physical appearance does not provide a valid taxonomic picture in microbes. Appearance evolves so rapidly that two closely related taxa may look wildly different and two distantly related taxa may look the same. This vexing problem was partially overcome in the 1980s through the use of rRNA-PCR (Table 1) . This method allows microorganisms in a sample to be phylogenetically typed and counted based on the sequence of their rRNA genes, genes that are present in all cell-based organisms. ”

“ Physical Constitution of Living Matter.—Microscopic examination does not take us much farther. The microscope, with the strongest magnification of which it is capable at present, shows us nothing beyond these links of aligned microsomes forming the species of protoplasmic thread or mitome, whose cellular body is a confused tangle or a very tangled ball. It is not probable that direct sight can penetrate much farther than this. No doubt the microscope, which has been so vastly improved, is capable of still further improvement. ”

“ The construction of the polype seems then to be confined to these glandular grains, to the viscous matter, and the invisible fibres which act upon the glareous substance.
The structure of the arms of the polypes is very analogous to that of their body. When they are examined by the microscope, either in a contracted or dilated state, their surface is shagreened; if the arm be much contracted, it appears more so than the body ”

“ As it is always desirable to examine the gathering on the ground, a “Gairdner’s hand microscope” with powers from 80 to 200 diameters will be found very useful. The best gatherings are those which represent one species abundantly. Those which are mixed may be rejected, unless they are seen to contain something valuable or important, as the object should be not so much to supply microscopical curiosities as to collect material which is available for the study of nature. ”

“ It becomes whiter and brighter with age, moves slowly round its axis, and may be perceived by the naked eye. But to the microscope the superficies of this pellucid membrane appears covered with molecules, as if it were granulated, which has occasioned some observers to imagine it to be hairy; the round pellucid molecules that are fixed in the center are generally largest in those that are young. The exterior molecules may be wiped off, leaving the membrane naked. When the young ones are of a proper size, the membrane opens, and they pass through the fissure ”

“ If a polype be carefully placed before the microscope, without wounding it, you will seldom be disappointed in seeing some of these grains detach themselves from the superficies thereof, and that even in the most healthy.
But if the grains separate themselves in large quantities, it is the symptom of a very dangerous disorder; the surface of the polype thus attacked becomes more and more irregular, and is no longer well terminated and defined as before. The grains fall off on all sides, the body and arms contract and dilate, it becomes of a white shining colour, loses its form as at a, Fig. ”

“ The announcement in a recent periodical of the discovery of soluble protoplasm emphasizes the existence of a vast unknown covered by the words protoplasm, enzymes, invisible organisms. Is it coincidence of fate that with the growing importance of the problem of the invisible organism there comes the invention of a microscope of surpassing excellence with which the seeing of molecules is a hoped for possibility? ”

“ A year later Miyoshi carried proof to demonstration, and showed that a fungus-hypha is actually so attracted by substances on the other side of a membrane, and that its tip pierces the latter; for the hyphæ were made to grow through films of artificial cellulose, of collodion, of cellulose impregnated with paraffin, of parchment paper, and even the chitinous coat of an insect, simply by placing the intact films on gelatine impregnated with the attracting substance, and laying the spores on the opposite side of the membrane. ”

“ Growing Cells have received more attention from those who devote attention to the lower forms of life, the construction of which, for the purpose of maintaining a continuous supply of fresh water to objects under observation, and for sustaining their vital energy for a long period, is of some importance. The employment of live-cells is resorted to by microscopists, as doubtless there is much to be discovered concerning the metamorphoses which some of the lower micro-organisms, both of plant and animal life, pass through. ”

“ They are principally carbon, hydrogen, oxygen, nitrogen, the elements of all organic compounds, to which may be added sulphur and phosphorus. At the head we have the albuminoid molecule, or the albuminoid molecules, aggregates of the preceding atoms. In the third stage the micellæ or tagmata, aggregates of albuminoids and water, are still too small to be observed by the senses. They unite in their turn to form the microsomes, the first elements visible to the microscope. The microsomes, cemented by linin, form the filaments or links which are called mitomes. ”

“ The industry of the caterpillar, in securing itself for its change into the chrysalis, must not be passed by; not only because it naturally leads the reader to consider and admire that divine agency, by which the insect is informed, but because the different modes it makes use of cannot be properly investigated, without the assistance of glasses, it therefore consequently becomes a proper subject for the microscope ”

“ The tree-vorticellas must ever stand first among all the varied and beautiful objects which the microscope reveals. A species common in New England and the Middle States is known scientifically by the name of Carchesium Polypinum. It is impossible to convey a true idea of its beauty from a dead black and white drawing. ”

“ As to their size, we can only say that they are far below the limits of visibility, and that even the minutest granules which we can barely perceive by means of our most powerful microscopes cannot be small individual biophors, but must be aggregates of these. On the other hand, the biophors must be larger than any chemical molecule, because they themselves consist of a group of molecules, among which are some of complex composition, and therefore of relatively considerable size. ”

“ The orifices of the cells are surrounded with teeth, and are usually furnished below with a very long bristle—the polypidom appearing to the naked eye as a white hairy crust. In the variety figured, the long bristles are replaced by a spine; and this is not uncommon.
The polypidoms of the Bryozoa form interesting microscopic objects, the cells being furnished with variously arranged spines and punctures or dots. In some the cells are erect and arranged in rows upon the branches of a plant-like stem, while in others they are scattered irregularly over a creeping filament. ”

“ What is important from the standpoint of mimicry is that these divisions, made solely on anatomical structure, correspond closely with the separation of models from mimics. Of the eight sub-families into which the Nymphalidae are divided four, viz. the Danainae, Acraeinae, Heliconinae, and Ithomiinae, provide models and some, but far fewer, mimics; two, the Satyrinae and Nymphalinae, provide many mimics and but few models, while two groups, the Morphinae and Brassolinae, practically do not enter into the mimicry story. ”

“ In studying under the microscope the development of these little organisms, in the preparations of which they have taken possession, a very curious evolution of one of the microbes of the air is revealed. The organism is a bacterium, which presents at first sight the characteristics of a very long, filamentous bacillus. M. Miquel affirms that he has seen this organism afterward divide itself into segments of unequal size, in such a way as to form strings of micrococci. The observation deserves consideration, for, if it is confirmed, and the ”

“ The support from two independent sources of phylogenetic information, our retroposon markers and nuclear genes [4] , [21] , [17] , invalidates the mitochondrial results [3] , [16] , [22] . Complete mitochondrial genomes can give misleading signals, as was demonstrated for the incorrect position of Monotremata among mammals [24] , and can even mislead phylogenetic reconstruction when mixed with nuclear data.
The position of Microbiotheria has been intensely debated since the cohort Australidelphia was first suggested based on tarsal evidence [1] . ”