46 



CHIM^ROID FISHES AND THEIR DEVELOPMENT. 



The grouping of the yolk elements in the mature egg is somewhat irregular. 

 Sometimes "drifts" of germinal yolk underlie the coarse yolk; sometimes they 

 extend obliquely, admitting between them inbursts of coarser yolk. In general, at 

 the time of fertilization, the germinal yolk dips deeply down into the coarse yolk, 



36 



I*. 



m 



31 



S 





35 



^^Ai^ik^^^ 





"■^ 



:*- 



:./ 



.-;'5 





Fig, 35. — Section of fertilization stage, showing near tfie surface and at tfie side of the germinal area a sperm which has just gained 

 entrance. This is shown at 5, surrounded by a hghter area of germinal material. In the depression above the sperm is a mucus- 

 like mass which may represent in part the tail of the sperm, w/, Middle piece. > 573. 



Fig. 36. — Section of fertilization stage, showing deep entrance pit of a sperm. From the lowermost point arise branching rays. 



Fig. 37. — Detail of section of specimen shown in fig. 34. From the path of a sperm astral rays branch in many directions, and at 

 various points (indicated by the dark points) new centers of radiation appear. 



Fig. 38. — Detail of fertilization stage shown in fig. 34. The present section follows almost exactly the entrance path of a sperm. The 

 latter appears at .s, and it is seen that the entrance pit is a delicate tube extending downward in the direction of a sperm. Around 

 the latter appears a well-marked aster, and in this neighborhood, strung along a prominent ray of the aster, are a number of deeply 

 stained " cenlrosomes." A similar "centrosome" occurs near the lowermost point of the entrance lufje of the sperm. 



forming a plug-shaped mass twice as deep as wide (fig. 34). This is possibly the 

 homologue of the Panderian nucleus figured in the shark egg; certain it is, how- 

 ever, that the egg of Chimaera has not as clearly a marked series of tunics in its 

 yolk arrangement. 



