1 86 



THE SPOROZOA 



axial filament which terminates in a deeply staining granule 

 placed just behind the nucleus. The male gametes become free 

 within the cyst and penetrate the female chamber, the rostrum 

 being directed in front. . They each seek out a passive female 

 gamete and unite with it, often when still incompletely developed 



FIG. 80. 



Development of the gametes, and fertilisation, in Stylorhynchus longicollis. Stein (par. Blaps 

 mortisaga). a, undiflerentiated gamete, still attached to the body of the parent gametocyte. 

 b, c, d, stages in the evolution of the motile male gamete ; the body elongates and becomes 

 prolonged posteriorly into a vibratile caudal filament, the nucleus being placed at the anterior 

 end, from which a short rostrum grows out ; from the distinct centrosome an axial filament is 

 prolonged through the body as far as the caudal filament, which appears to be a continuation 

 of the axial filament ; a prolongation of the axial filament in the opposite direction runs round 

 the nucleus and forms the axis of the rostrum (Leger). The fully mature gamete, d (" sperma- 

 tozoid," Leger), has the nucleus very condensed and the axial thread doubled, both in the 

 body and in the rostrum ; but as a rule the conjugation is hastened and takes place when the 

 male gamete is in the still immature stage shown in c ("spermatid" of Liger). e, mature 

 female gamete, only differing from a in the loss of the stalk attaching it to the parent body. 

 /, a "spermatid" conjugating with a female gamete, g, later stage of the conjugation ; the 

 protoplasm of the two gametes has fused into a spherical mass and the nuclei are fusing, h, 

 zygote (sporoblast), with single nucleus, t, spore, with spore-membrane and single nucleus 

 preparing for division. (After L6ger, x 1900.) 



(Fig. 30, /). The flagellum drops off, but the bodies and nuclei of 

 the gametes fuse and the zygote forms a spore in the usual way 

 (Fig. 30, g, h, i). The conjugation occurring here is remarkable 

 in that the gametes are the opposite, in some points of their 

 equipment, to the general type of differentiation in anisogamy, 

 since the active male element is as large or larger than the passive 

 female, and as well provided with reserve material. In Pterocephalus, 



