1908] YAMANOUCHI— SPERMATOGENESIS AND OOGENESIS 173 



Fig. 20. Polar view of stage shown in fig. ip; 66 chromosomes evident. 



Fig. 21. Late telophase; spermatid mother cell has divided into two sperma- 

 tids, each containing a single blepharoplast near concave side of young nucleus; 

 Nebenkern near each nucleus. 



Fig. 22. One of the spermatids after the cellular connection has become 

 loose and the regular arrangement has been lost; nucleus larger; chromatin 

 reticulum composed of ragged clumps and two nucleoli present; blepharoplast 

 applied very close to nuclear membrane; Nebenkern a little apart from the mem- 

 brane. 



Figs. 23, 24. Two different views of same stage; fig. 23 shows surface of 

 blepharoplast; fig. 24 the cross-section; Nebenkern moved near nucleus after 

 blepharoplast has begun to grow and elongate. 



Figs. 25-27. Three different views of the same stage; fig. 25 shows part of 

 surface view; fig. 26 longitudinal section; fig. 27 cross-section. 



Fig. 28. Nucleus of spermatid has become spiral; free end of blepharoplast 

 wedge-shaped, the other end gradually tapering and along one edge a tapering 

 end of the nucleus runs from the opposite direction and coalesces. 



Fig. 29. Stage of spermatid nucleus later than that in fig. 28; coiled form of 

 nucleus farther advanced; one end of nucleus, consisting chiefly of the blepharo- 

 plast, clearly visible; the other end, terminating in a sausage-shaped structure, 

 slightly recognizable in the center below the Nebenkern, which is drawn lightly. 



Fig. 30. Stage similar to that shown in fig. 29, viewed from different direction; 

 end of nucleus terminating in sausage-shaped structure visible. 



Fig. 31. Almost mature sperm within a spermatid; whole structure of 2.75 

 coils, of which 1 . 2 coils are blepharoplast, the rest the nucleus that terminates in 

 a blunt end; long cilia borne on outer surface of blepharoplast; Nebenkern not 

 drawn . 



Fig. 32. Optical section of side view of stage shown in fig. 31; Nebenkern 

 larger and near blunt end of sperm. 



Fig. 33. Sperm fixed in free swimming condition; anterior end consists of 

 blepharoplast which gradually covers only outer surface, and is replaced by band 

 structure of nuclear substance which finally ends in a sausage form; Nebenkern 

 present within vesicle. 



PLATE VII 



Oogenesis 



Fig. 34. Cross-section of part of prothallium where cushion region arises later; 

 nucleus in telophase of mitosis which forms archegonium initial. 



Fig. 34a, Nucleus shown in previous figure under higher magnification. 



Fig. 35. Nucleus of archegonium initial in metaphase of mitosis which cuts 

 off basal cell. 



Fig. 35a. Nucleus shown in fig. 35 under higher magnification. 



Fig. 36. Division into central cell and primary neck cell. 



Fig. 37. Central cell or primary oogenous cell. 



