250 THE SPOROZOA 



digested by it Culex, on the other hand, is the intermediary for 

 the Haemoproteus ( = Proteosoma) of birds, and when it bites a bird 

 infected with this genus of parasites, it digests all the stages except the 

 gametocytes. Cukx, in fact, stands in the same relation to the malarial 

 parasites of birds, as Anopheles to those of man. Should an Anopheles, 

 on the other hand, bite a bird infected with Haemoproteus, it will 

 digest every stage of the parasite, gametocytes and all. 1 



In the spherical microgametocyte ("sperm-mother-cell," Lan- 

 kester) the nucleus breaks up and the fragments of chromatin 

 travel to the periphery (Fig. 68, IXa). From Schaudinn's observa- 

 tions upon Haemoproteus it would appear that a karyosome is left in 

 the centre of the body, as in Coccidium. The surface of the body 

 grows out into long thread-like processes, usually four to six 

 in number, each extremely motile and resembling in its movements 

 a flagellum. Hence the parasite at this stage is known as the 

 Polymitus form, since it was regarded by some earlier observers as 

 a Flagellate belonging to that genus. The entire chromatin sub- 

 stance of the microgametocyte passes into the so-called flagella, 

 which are in reality the microgametes ("spermatozoa," Lankester). 

 They are formed very rapidly, and by their active movements 

 soon become detached from the body of the gametocy te, which, like 

 that of the Coccidia, is completely enucleated, except for its 

 karyosome, and perishes as residual protoplasm, together with the 

 contained melanin-granules. Each microgamete is a slender 

 filament, slightly thickened in its middle portion, where is lodged 

 the chromatin which composes the greater part of its substance. 

 Like the microgametes of Adelea and Benedenia amongst Coccidia, 

 it has no true flagella, but progresses actively by serpentine move- 

 ments of the body in quest of a macrogamete. 



In the macrogametocytes also the development is on the same 

 type as in Coccidia. The schizogony is completely suppressed, 

 and each macrogametocyte becomes a macrogamete after having 

 gone through a process of maturation by ejecting a portion of its 

 nucleus (Fig. 68, X>). It is then ripe for fertilisation. 



The gametes conjugate in a manner essentially similar to that 

 described above in Coccidia. After the microgamete has pene- 

 trated the macrogamete, the two pronuclei fuse into a single 

 nucleus (Fig. 68, XI, XII). The zygote at first has the form of 

 a sphere, but soon after fertilisation it becomes elongated and 

 spindle-shaped, and grows into a small worm -like, or rather 

 gregarine-like body, which is actively motile, and has been 



1 Schaudinn believes, with Grassi, that in some cases the Anopheles may be 

 naturally immune against the malarial parasite, and that such immunity, if acquired 

 by a whole race of the mosquito, would account for the disease having died out in 

 localities where it was formerly abundant, as in the eastern counties of England, for 

 example. 



