1 84 



BULLETIN OP THE BUREAU OF FISHERIES. 



I ^m^m 



Fig. 176.— Sector from a male follicle prepared on April 1. X 900. Fixed in Flemming fluid and stained with Heidenhain 

 iron hematoxylin. Spc, sperm mother cells or specmatocytes on wall of follicle; Spd, spermatids in center of follicle. 



Fig. 177.— Longitudinal section through a minor genital canal of a female mussel. X 765. Preparation same as fig. 176. 

 CEp, ciliated epithelium which lines one side of canal only; GC, genital canal, containing a ripe ovum; GE, germinal epithelium 

 containing developing ova. 



Fig. 178.— Longitudinal section through a freshly laid egg that has not been fertilized. The spindle of the first polar body is 

 formed and does not pass beyond this stage normally unless the egg is fertilized. Fixed in Bouin fluid and stained with Heiden- 

 hain iron hematoxylin and congo red. 



Fig. 179.— Longitudinal section through an egg showing the condition which follows immediately after impregnation. 

 X 900- Head of spermatozoon, Sp, enlarges greatly as it migrates toward center of cell At same time spindle of first polar body- 

 passes into anaphase stage and process of maturation continues rapidly from this time on until completed. Preparation same 

 as fig. 176. 



Fig. 180. — Longitudinal section through an egg showing spindle of second polar body which is formed immediately after 

 first polar body is extruded. Preparation same as fig. 178. 



