Triptolemus

“ Similarly with regard to the many other pathogenic Trypanosomes now known, there is undoubtedly, in each case, some indigenous wild animal tolerant of that particular form, which serves as a “latent source of supply” to strange mammals.
The transmission of the parasites from one vertebrate individual to another is effected, in the great majority of cases [3] by a blood-sucking invertebrate, and by this means minion; alone. The “carrier” of a Trypanosome of warm-blooded vertebrates is, in all instances so far described,Transmission: Alterations of Hosts. ”

“ Different genera and species of the trilobite are now found in almost every part of the globe, and are frequently exceedingly abundant in the rocks which contain them. That they must have swarmed in particular places, is abundantly evident from a number of localities in our own country,—millions, for example, must have lived and died not far from Trenton falls, in the State of New York. ”

“ Trypanosomes vary greatly with regard to size; even in one and the same species this variation is often noticeable, especially under Mon, , w, oD, different conditions of life. The common Trypanosoma rotatorium of frogs (fig., A and B) is, taking it all in all, one of the largest forms so far described. Its length (inclusive of the flagellum) varies from 40-60 p, while its greatest width (including the undulating-membrane) is from 8-30, a; in the very wide individuals breadth is gained more or less at the expense of length. ”

“ One flagellum is entirely free and directed forwards; the other at once turns backwards and is attached to the convex or dorsal side of the body for the greater part of its length. In all other Trypanosomes there is only one Hagellum, which is invariably attached to the body in the same manner as the posterior one of bi flagellate forms. ”

“ This species has been shown by Kinghorn and Yorke, and also by Bruce, to be responsible for the transmission of Trypanosoma rhodesiense, the micro-organism producing sleeping sickness in man in Rhodesia and Nyasaland and also in parts of German and Portuguese East Africa. Fisher and Taute have demonstrated experimentally that Trypanosoma gambiense—the sleeping sickness parasite of other parts of Africa—may also be transmitted by this fly, and in addition it is known to be capable of disseminating several species of trypanosomes pathogenic to animals. ”

“ The ancestor of the trilobite is believed to have been a soft-bodied, free-swimming, flat, blind or nearly blind animal of few segments, because:
(a) the form of both adult and embryo is of a type more adapted for floating than crawling;
(b) the large pygidium is shown by ontogeny to be primitive, and the elongate worm-like form secondary;
(c) the history of the trilobites shows a considerable increase in the average number of segments in successive periods from the Cambrian to the Permian ”

“ As pointed out in the case of Calymene and Ceraurus, the trilobites show a tendency toward the degeneration of the first and second pairs of biramous appendages, particularly of the gnathobases. They are in just that stage of the backward movement of the mouth when the function of the antennæ as mandibles has not yet been lost. If the presence of functional gnathobases back of the mouth, rather than the points of attachment in front of the mouth, is to be the guide, then Triarthrus might be classed as an arachnid and Calymene and Isotelus as crustaceans. ”

“ The small Trypanosomes resulting from either of these modes of division differ from typical adults by their stumpy, pyriform shape, the position of the kinetonucleus near the flagellar end of the body, and the absence, during the first part of their youth, of an undulating-membrane. At this period they have, in fact, what may be termed a “pseudo-Herpetomonadine” aspect. These young individuals can themselves multiply by equal binary fission, giving rise to little fusiform parasites; with growth, these gradually assume the adult appearance. ”

“ Very many of the common domestic mammals can be successfully infected (either thus accidentally or else on purpose) with different “pathogenic” Trypanosomes, to which they succumb more or less readily, but they cannot be regarded as the natural hosts of those Trypanosomes. In dealing with disease-causing forms, the more narrowly the original source of the parasite concerned is defined, the closer do we get to the true vertebrate host or hosts. ”

“ Agglomeration consists in the grouping or union together of several Trypanosomes around a common centre; this leads to the formation of rosette-like clusters, or even of large masses composed of several rosettes. The end by which the parasites join is typically, in the case of Trypanosoma, the non-flagellate (anterior) end. If a favourable change in the surrounding medium sets in, the Trypanosomes are able to undergo the reverse process, namely dis agglomeration; the parasites liberate themselves and the rosette is dissolved. ”

“ Trilobites, as a group, seem to have adapted themselves to almost all conditions of marine life: « 223 » some are found in the hardened black mud of shallow waters, whilst others are to be looked for in the limestones and excessively fine sediments of deeper waters. In all probability certain of these forms crawled over the soft, oozy sea-bed in order to obtain their food, and consequently their remains in the stratified rocks would be restricted to the fine black shales; whilst the freely swimming forms could change their habitat at will, and would be found alike in sandy or clayey deposits. ”

“ The development of an indifferent ookinete into an indifferent Trypanosome is shown in fig. 7, from which it will be seen that the cytological details are very complex, The indifferent parasites exhibit an alternation of resting, attached phases with active periods, during which they multiply actively and become very abundant in the insect. The male forms, which are very small and the homologies of the micro gametes developed in the blood, appear to die off soon. The female Trypanosomes, on the other hand, grow to a large size, laying up a store of reserve nutriment. ”

“ Apparently the Trypanosoma can live in the blood without doing much harm, and only when it reaches the cerebro-spinal canal does it set up the sleeping-sickness. It is also found in great numbers in the lymphatic glands, especially those of the neck, which in patients infected by the parasite are usually swollen and tender. From the similarity of the parasite to that causing the cattle disease of South Africa, the idea at once arose that the Trypanosoma was conveyed from man to man by a biting insect. ”

“ That organic remains furnish us with the most satisfactory evidence of the identity or dissimilarity of certain formations, is a disputed point with some geologists [45] It cannot reasonably be doubted, that new and isolated facts have been made the basis of a too hasty generalization. On this subject Count Rasoumowsky makes the following remarks:—"Les divers gisemens des Trilobites ne me semblent pas non plus pouvoir être déterminés avec quelque précision. ”

“ While the evidence [147] is far from clear, it would appear that the discovery of animals with the form of Limiting and the eurypterids and the appendages of trilobites means something more than descent from similar ancestors. Biramous limbs of the type found in the trilobites would probably not be evolved independently on two lines, even if the ancestral stocks were of the same blood.
The Aglaspidæ, as represented by Molaria and Habelia in the Middle Cambrian, are quite obvious closely related to the trilobites easily derived from them, and retain numerous of their characteristics. ”

“ A skull from the Upper Triassic Karoo beds of South Africa described as Tritylodon longaevous, which has multituberculate molar teeth, was also at first placed in this group, but has been subsequently regarded as a reptile, although Dr R. Broom considers that the original determination is correct. Possibly a fore-limb from the same formation described as Theriodesmus phylarchus indicates a similar or allied animal. Not improbably Tritylodon indicates a direct link between the multituberculate mammals and the anomodont reptiles of the Permian and Trias. ”

“ The pygidium of trilobites is compared with the metasomatic shield of Limulus. No homology, if homology is intended, could be more erroneous. The metasomatic shield of Limulus is, as shown by ontogeny and phylogeny, formed by the fusion of segments formerly free, and includes the segments between the cephalic and anal shields, or what would be known as the thorax of a trilobite. ”

“ The buckler of this species is irregularly hemispherical; the front pyriform and without pustulations. The cheeks are almost entirely occupied by the eyes, which are placed very near each other on the upper part of the forehead; are very large and trilobate, the side lobes being elongated and attenuated in front. The articulations of the back are twenty in number, those of the abdomen not being distinguishable from those of the tail. The costal arches of the side lobes are round near their extremities, and are intersected with two or three raised lines. ”

“ An additional point to be brought forward to show that the trilobites probably pass the greater part of their life on their back, and died in that attitude, is that the young Limulus generally feed while turned on their back; moving at an angle with the bottom, the hind extremity raised, they throw out their feet beyond the anterior edge of the carapace, browsing, as it were, upon what they find in their road, and washing away what they do not want by means of a powerful current produced by their abdominal appendages. ”

“ Turtles became well established during this period (Psammochelys, Chelyzoon) . Of great interest is the discovery of the earliest traces of mammals in the Trias of Europe, South Africa and North America. The imperfect remains (teeth and jaw-bones) do not admit of any certainty in deciphering their relationships. Microlestes from the Rhaetic of England and Württemberg and Dromatherium from North America are perhaps the best known; Tritylodon from South Africa may also be added. Among the lower forms of marine life foraminifera and sponges play a subordinate part. ”

“ The fossil remains of the trilobite family, are supposed by most naturalists to belong to a race of beings now extinct; but from the strong analogy which exists between them and certain species of crustaceous animals now living, it is highly probable that they will yet be found alive. ”

“ Trypanosomes are harboured by members of all the chief classes of vertebrates with the exception of cyclostomes. By far the greater number of hosts are furnished by fishes, birds and mammals. Among batrachians the parasites have been found, up till now, only in frogs; and among reptiles their occurrence has only been observed in one Occurrence. ”

“ Trypanosomes occur in the blood of representatives of all the vertebrate classes. Often the trypanosomes occur so scantily in the blood that they are overlooked on examination. A useful aid in detecting the flagellates in such cases consists in the use of cultures of the blood of the host on artificial media. Stimulated by the medium multiplication occurs, and hence the parasites are more easily detected. [For the composition of such culture media see Appendix.] ”

“ In most Trichoptera the veins of the hindwings are much more numerous than those of the fore-wings, in the Micropterygina they are usually equal in number, in other Lepidoptera they are less numerous; in the course of descent there has therefore been a greater progressive diminution in the number of veins of the hind-wings as compared with those of the fore-wings, though these also have diminished. ”

“ By "whole ones" perfect individuals are not meant, for before they became fossils the wear and tear of their time and the process of decomposition had taken away all the softer parts and even most of the harder exterior covering. What is usually preserved and revealed to us when the trilobites weather out of the embrace of their entombing rocks is the test, the hard shell of the upper or dorsal side. ”

“ Subsequent growth results in the production of the typical trypanosome form, which re-enters the circulating blood and multiplies by longitudinal binary fission. Division of the parasite prior to the formation of a latent body may occur and division of the latent forms themselves is known, though less common. ”

“ Trypanoplasma, Laveran and Mesnil, 1901, with a kinetic
nucleus and undulating membrane.
Of these genera Prowazekia must be discussed. Bodo does not occur in man. Species of Trypanoplasma occur in the blood and in the gut of various fishes, in the seminal receptacle of certain snails, in the gut and genitalia of a flatworm (Dendrocœlum lacteum) and in the vagina of a leech. Closely allied to Trypanoplasma is the genus Trypanophis, parasitic in the cœlenteric cavity of Siphonophores. ”

“ The disease is transmitted by the bites of several species of assassin-bugs, or Reduviidæ, notably by Conorhinus megistus. The evolution of the parasite within the bug has been studied especially by Chagas and by Brumpt. From the latter's text we take the following summary.
The adult trypanosomes, ingested by a Conorhinus megistus, of any stage, first change into Crithidia-like forms and then those which remain in the stomach become ovoid and non-motile. ”

“ African sleeping sickness is caused by a protozoan para- site of the genus Trypauosoma that lires in the blood and other body liquids. Trypanosomes are active, one-celled organisms having one end of the body prolonged into a tail, or flagellum. ”