Potidaea

“ In collections of insects from India or Ceylon it is not unusual to find specimens of the A form of female of polytes placed with P. aristolochiae, and the H form with P. hector. When the insects are old and faded and pinned out on cork the mistake is a very natural one. But after all the enemies of polytes do not hunt it in corked cabinets, and any estimation of resemblance to be of use to us must be based upon the living insects. ”

“ POTAMIDES SUB-CARINATUS (Plate VII.) .—Fig. 13 (late Cerithidea subcarinata) is a dull black shell seldom over half an inch long. The colour is usually concealed by the reddish-brown epidermis. The interior is dark purple.
POTAMIDES BICARINATUS (Plate VII.) .—Fig. 19 (late Cerithidea bicarinatus) is a reddish-brown or purple shell, covered with a blue or brown epidermis. The interior is purple. It is found in the North Island in large numbers on banks of sand mixed with mud near high water mark. Its extreme length is one inch. ”

“ All over Canada and the Northern States there grows a third and very common potentilla, the cinque-foil or "five-finger" of popular botany (P. Canadensis) , a pretty, prostrate, creeping weed, with golden yellow flowers springing close to the ground, and five leaflets instead of three to each leaf. Ever since the days of Linnæus this plant has been considered distinct from the common European cinque-foil (P. reptans) , and the differences are certainly sufficient to justify their division as separate species, as systematic botany goes nowadays. ”

“ It is also found in the earliest and most primitive form of larva, known as the Nauplius. As a rule the protopodite is composed of two segments, though one may be reduced or suppressed and occasionally three may be present. In many cases, one of the branches, generally the endopodite, is more strongly developed than the other. Thus, in the thoracic limbs of the Malacostraca, the endopodite generally forms a walking-leg while the exopodite becomes a swimming-branch or may disappear altogether. ”

“ For example, each of the three forms of polytes female holds its own and all must, therefore, be regarded as equally well adapted to the circumstances under which they live. They are so distinct in colour that it is difficult on this hypothesis to suppose that they are all on the same footing in respect to their environment. Yet if one is better off than the others, how is it that these still exist? ”

“ Further, they are developed from the upper surface of the body. Now, in the Annelids the limbs are typically double pairs projected from the sides of the body; the parapodia consist of two branches, notopodium and neuropodium, and the gills when present are modifications of the notopodium. In the Crustaceans this bipartite condition is indicated by the exopodial and endopodial divisions of the limbs. In the adult insect this duplicity has disappeared, unless we recognise in the position of the gill tracheæ the equivalent of the branchiferous notopodium. ”

“ As I observed that insects are often caught in this clammy secretion, exactly as in the case of the common catchflies (Silene noctiflora Virginica, regia, etc.) , I have not the least doubt that the potentilla eats and digests the creatures it entraps, in order to supply it with nitrogenous material for its own pollen, ovules, and seeds. This is the more probable, as the clamminess increases near the flower-buds and blossoms, and is scarcely at all noticeable near the base of the stem. ”

“ Caladium and Pothos are exclusively forms of the tropical world; the species of Arum belong more to the temperate zone. Arum italicum, A. dracunculus, and A. tenuifolium, extend to Istria and Friuli. No Pothos has yet been discovered in Africa. India has some species of this genus (Pothos scandens and P. pinnata) which are less beautiful in their physiognomy, and less luxuriant in their growth, than the American species. ”

“ I trust, before long, that some naturalist, with more skill than I possess, will examine these parasites on Scalpellum vulgare, which unfortunately is the only species of the genus that can be easily obtained. Fresh specimens, or those preserved in spirits of wine, are necessary. The action of boiling caustic potash is very useful in cleaning the prehensile antennæ. If these latter organs are sought in the hermaphrodite for the sake of comparison, young specimens, adhering to clean branches of a coralline, should be procured, and caustic potash used. ”

“ Besides these external movements, there are internal movements revealed by the contained granules, which stream freely in the more fluid interior. Those Protista that, while exhibiting amoeboid movements, have no clear external layer, such as the Radiolaria, Foraminifera, Heliozoa, etc., present this streaming even at the surface, the granules travelling up and down the pseudopodia at a rate much greater than the movements of these organs themselves. In this case the protoplasm is wetted by the medium, which it is not where there is a clear outer layer: for that behaves like a greasy film. ”

“ Pulmonata.—Intermediate between the essentially fresh-water and the essentially marine species come the group sometimes known as Gehydrophila, consisting of the two families Auriculidae and Otinidae. These may be regarded as Mollusca which, though definitely removed from all marine species by the development of a true lung or lung cavity in the place of a gill, [18] have yet never become, in respect of habitat, genuine fresh-water species. Like Potamides, they haunt salt marshes, mangrove swamps, and the region about high-water mark. ”

“ The Sessiliventres are plant-eaters; their larvae (Fig. 343, A) are provided with legs, and are able to procure their vegetable food for themselves. The larvae of the Petiolata are maggot-like and helpless, and are dependent for food on supplies afforded them by their parents or companions. It is said by Dewitz that although the larvae of the Petiolata appear to be legless, there are thoracic legs within the body. ”

“ As the sensitiveness is here greater than in any other species of the genus observed by me, and is in itself remarkable, I will give fuller details. The petioles, when so young that they have not separated from each other, are not sensitive; when the lamina of a leaflet has grown to quarter of an inch in length (that is, about one-sixth of its full size) , the sensitiveness is highest; but at this period the petioles are much more fully developed proportionally than the laminæ of the leaves. Full-grown petioles are not in the least sensitive. ”

“ The brackish-water beds contain Potamomya plana, Cerithium mutabile, and Potamides cinctus (Fig. 37) , and the marine beds Venus (or Cytherea) incrassata, a species common to the Limburg beds and Grès de Fontainebleau, or the Lower Miocene series. The prevalence of salt-water remains is most conspicuous in some of the central parts of the formation.
Among the shells which are widely distributed through the Headon series are Neritina concava (Fig. 177) , Lymnea caudata (Fig. 178) , and Cerithium concavum (Fig. 179) . ”

“ Its form is not constant during activity, for fingerlike processes called pseudopodia are pushed out tentatively in many directions to be followed as circumstances direct by the materials of the whole cell body. Other protozoa differ in possessing constant forms, or in having constant vibratile processes, or shells of some kind, while in still other cases like individuals combine to make colonies which are more or less definite and permanent. Here at the very foot of the organic scale are found animals which seem to be entirely different from those above. ”

“ The tissues and shell are transparent, permitting observation of the internal organs. In the Pterotrachaeidae the foot takes the form of a fan-shaped disc, usually furnished with a sucker. The body is compressed at the posterior end, often with a ventral “fin.” In Atlanta the foot consists of three very distinct parts: a propodium, a mesopodium, on which is a small sucker, and a metapodium, which carries the operculum. The branchiae are carried on the visceral sac, and are free in Pterotrachaea, slightly protected by the shell in Carinaria, and entirely covered in Atlanta ”

“ The alternation of limestone conglomerates and shales in the lower Potosi series indicates near-shore conditions of sedimentation, and the occurrence of the single specimen of a eurypterid, far from pointing to a marine habitat for this one individual, militates very strongly against such a mode of life. In all cases the occurrence of a single individual is one of the strong arguments against the assumption that the individual belongs to the fauna of the bed in which it is found. ”

“ He selected birds for the special subject of his first investigations in the field, and his monograph on the kidneys of birds attracted widespread attention among the scientists of Europe. As the farthest removed from man of the beings that are warm-blooded, these creatures have always attracted particular attention, and, quite apart from any interest in evolution, were the subject of special investigation. Owing to the facility with which they can be studied in embryonic stages in the hatching egg, most of the peculiarities of their structure and development are very well known now. ”

“ How the potentilla digests its food I do not know, but long observation has fully convinced me that whenever a plant has viscid, glandular hairs or secretions upon its penduncles, pedicels, calyx, and flower-buds, it is invariably an insect-catcher, and an insect-eater too. ”

“ Potamogeton is an extensive genera of water-plants, numbering not less than fifteen species in the brooks and rivers of this country alone. P. fluitans, crispus, and densus, are most easily obtained, and they flourish in the tank, and make rich branching masses for the centre, or to climb over rockwork. They are all rather coarse and apt to shed their lower leaves, but, if well placed, produce a striking effect. They blossom freely in the aquarium, and that is a great recommendation. ”

“ Podeon: in Hymenoptera, the petiole: the true second abdominal segment.
Podex: the upper plate of the anal opening; = supra-anal or sur-anal plate in caterpillars.
Podical plates: the latero-ventral plates attached to the loth abdominal segment of Orthoptera; the two pieces on each side of the vent, thought by Huxley to be rudiments of an 11th abdominal ring; united they form the tergite of a rudimentary ring: = anal valves: paranal lobes.
Pododunera: apterous insects with biting mouth structures.
Podotheca: that part of pupa that covers the legs of future adult. ”

“ This reasoning would argue that Procyon cancrivorus probably enjoys higher, rather than lower, than expected rmax.
Potos flavus.—In addition to a low Ḣb, this species possesses other characteristics that limit its reproductive potential: low-quality diet, delayed reproduction, and birth of a single young each year. Because there does not appear to be any other feature of its life history that can counteract the influence of these factors, rmax in Potos flavus has evolved to be only 48% of expected (0.30; Table 10) . ”

“ The present species cannot twine spirally, which seems mainly due to the rigidity of the stem. In a very young plant, which did not revolve, the petioles were not sensitive. In older plants the petioles of quite young leaves, and of leaves as much as an inch and a quarter in diameter, are sensitive. A moderate rub caused one to curve in 10 m., and others in 20 m. They became straight again in between 5 hrs. 45 m. and 8 hrs. Petioles which have naturally come into contact with a stick, sometimes take two turns round it. After they have clasped a support, they become rigid and hard. ”

“ Gasteropoda.— (1) Operculate. Canidia and Clea are closely allied, with but little modification, to the marine Cominella [23] (Fig. 11) , as is also Nassodonta to Nassa. They occur (in fresh water) in the rivers of India, Indo-China, Java, and Borneo, associated with essentially fresh-water species. Potamides, with its various sub-genera (Telescopium, Pyrazus, Pirenella, Cerithidea, etc.) , all of which inhabit swamps and mud-flats just above high-water mark in all warm countries, are derived from Cerithium (Fig. 12) ; Assiminea, Hydrobia, and perhaps Truncatella, from Rissoa. ”

“ One of the weirdest of living mammals is the potto—“ghost monkey”, of West African jungles. It is about the size of a squirrel, with soft, yellow fur and protruding yellow eyes which shine like malevolent witch lights in the darkness of the jungle nights. The potto is a nocturnal animal of the tree tops. Its weird, whimpering cries are believed by natives to be the voices of evil spirits. The little creature is an aberrant member of the family of lemurs, ancient offshoots of the same family from which sprang the monkeys and great apes. ”

“ Very usually, but not universally, the metapodium carries an operculum. The division of the foot into lobes is a simple case of that much greater elaboration or breaking up into processes and regions which it undergoes in the class Cephalopoda. Even among some Gastropoda (viz. the Opisthobranchia) we find the lobation of the foot still further carried out by the development of lateral lobes, the parapodia, whilst there are many Pectinibranchia, on the other hand, in which the foot has a simple oblong form without any trace of lobes. ”

“ There is little doubt but that all wind-fertilised angiosperms are degradations from insect-fertilised flowers.... Poterium sanguisorba is anemophilous; and Sanguisorba officinalis presumably was so formerly, but has reacquired an entomophilous habit; the whole tribe Poterieae being, in fact, a degraded group which has descended from Potentilleae. Plantains retain their corolla but in a degraded form. ”