failed to appreciate its true significance, and considered it rather as a degeneration-appearance. The micro-gametes soon liberate themselves from the residual cytoplasm of the parent and swim away in search of a megagamete; each is a very slender, wavy filament, composed largely of chromatic substance. The finer details of structure of the microgamete of a malarial parasite cannot be said, however, to be thoroughly known, and it is by no means impossible that its structure is really trypaniform, as, according to Schaudinn’s great work, is the case with the merozoites and sporozoites.
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| From Lankester’s Treatise on Zoology. | ||
| Fig. 1.—Diagram of the complete life-cycle of the parasite of pernicious malaria, Laverania malariae, Gr. et Fel. The stages on the upper side of the dotted line are those found in human blood; below the dotted line are seen the phases through which the parasite passes in the intermediate host, the mosquito. Plan and arrangement chiefly after Neveu-Lemaire; details of the figures founded on those of Grassi, Schaudinn (Leuckart’s Zoologische Wandtafeln), Ross and others. | ||
I.-V. and 6-10 show the schizogony. |
VII., a, Male crescent. IX., a and b, Spherical gametocytes;in the male (IX. a) the nucleus has divided up. X., a and b, Formation of gametes; in the male (X. a) the so-called flagella or male gametes (fl) are thrown out, one of them is seen detached; in the female (X. b) a portion of the nucleus has been expelled. XI., A male gamete penetrating a female gamete at a cone of reception formed near the nucleus. XII., Zygote with two pronuclei in proximity.XIII., Zygote in the motile stage (vermicule or oökinete). |
XIV., Encysted zygote (oöcyst). |
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| From Lankester’s Treatise on Zoology. | |||
| Fig. 2.—Stomach of a mosquito, with cysts of Haemosporidia. (After Ross.) | |||
| oes, | Oesophagus. | Mt, | Malpighian |
| st, | Stomach. | tubules. | |
| cy, | Cysts. | int, | Intestine. |
The megagametocyte becomes a megagamete directly after a process of maturation, which consists in the expulsion of a certain amount of nuclear substance. The actual conjugation is quite similar to the process in Coccidia, and the resulting zygote perfectly homologous. In the present case, however, the zygote does not at once secrete an oöcyst, with a thick resistant wall; on the contrary, it changes its shape, and becomes markedly gregariniform and active, and is known for this reason as an ookinete. The ookinete passes through the epithelial layer of the stomach, the thinner and more pointed end leading the way, and comes to rest in the connective tissue forming the outer layer of the stomach-wall (fig. 2). Here it becomes rounded and cyst-like, and grows considerably; for only a thin, delicate cyst-membrane is secreted, which does not impede the absorption of nutriment. Meanwhile, the nucleus has divided into several, around each of which the cytoplasm becomes segmented. Each of these segments (“blastophores,” “zoidophores”) is entirely comparable to a sporoblast in the Coccidian oocyst, the chief difference being that it never forms a spore; moreover the segments or sporoblasts in the oocyst of a malarial parasite are irregular in shape and do not become completely separated from one another, but remain connected by thin cytoplasmic strands. Repeated multiplication of the sporoblast-nuclei next takes place, with the result that a great number of little nuclei are found all round the periphery. A corresponding number of fine cytoplasmic processes grow out from the surface, each carrying a nucleus with it, and in this manner a
