680 DK. n. n. faxtjiam ox the [Mny 3, 



2Vi6 Mid'ogainetocyte and Mia'oyameies. 



The microgametocyte * (PI. LVII. fig. 37) is an ovoid cell abont 

 13// long and 8 ^t broad in the specimens that I have seen. It 

 possesses a central nncleus containing a karyosonie. The process 

 of the formation of the microganietes of A', aviani is as follows: — 

 The chromatin of the nucleus, largely concentrated in the 

 karyosome, bieaks up (figs. 38-40) into minute granules or 

 chromidia which pass towards the surface of the cell, where they 

 appear to form a very fine chromidial network (fig. 38). The 

 chromidia then collect into groups or patches, arranged in the 

 form of minute, irregular loops with central hollows (figs. 38, 39). 

 These chromatic loo))s form a number of minute, flexible, I'od-like 

 bodies, composed almost entirely of clu'omatin (figs. 41-45). 

 These are the young microgariietes (figs. 43-46). The adult 

 microgametes are small parasites, their chromatic bodies measuring 

 3 yu to 4yu, in length, possessing a rod-like, somewhat curved liody 

 composed of a core of chromatin which is surrounded by a 

 tenuous film of cytoplasm, prolonged outw'ards to form two fine 

 flagella (figs. 44, 46). The flagellum Avhich I term the posterior 

 flagellum trails behind the organism and is practically a con- 

 tinuation of its body ; the other flagellum is at the opposite end 

 of the body and so is termed the anterior flagellum. In life, the 

 microgametes are capable of serpentiform movements. Owing 

 to the minute size of the microgamete (about 3 /x to 4 /a long) 

 it is only with the greatest difliculty that the flagella can be 

 discerned. 



The whole of the microgametocyte is not used in the for- 

 mation of the microgametes. "When separation of the mici'o- 

 gaiiietes from their mothei- cell occurs, a large amount of the 

 l)ody-substance of the latter remains as a somewhat faint staining 

 i-esiduum, in which the pale staining remains of the kai-yosome 

 (Hg. 43, cf. fig. 38) can sometimes be distinguished. The residiuuu 

 takes no further part in the vital activities of the paiasite. 



The microgametes are set free into the lumen of the gut and 

 proceed to seek out the macrogametes. 



(d) Fertilisation. 



When the macrogamete has attained its maxinnim development, 

 it often lies in the ei»ithelium, near the miter edge of the tissue, 

 or may even burst thiough the attenuate wall of the host-cell 

 and so n^ach the margin of the lumen of the gut. The minute 

 but active microgametes (PI. LYU. fig. 46) meanwhile have bwken 

 away from the residual jn-otoplasm of the host-cell, and swum out 

 will) rapi<l lashing movements of their flagella into the gut. 

 Here llicy ai'e attracted, possibly liy some cliciuiotaciie substance, 



* Uniimclt'iitr niicroftainotocytos srt'iiiecl nuc in iiit'paiatiaiis, I'oi- tlii' I'lll rniiidly 

 procecvls to form many mic-ropaniptcs. 



