IQQ J. Moore, 



its rudiment. It is possible that further details as to the later condi- 

 tion of these parts might be obtained by the studj^ of macerated 

 specimens, but I have not yet tried them. 



While these changes progress in the minute structures of the 

 spermatid, the better known phenomena of maturation are passed 

 through — terminating in the discharge of the residual corpuscles into 

 the lumen of the tubule — and the spermatozoa are then practically, 



complete. 



Concluding remarks. 



From the results of these observations on the genesis of the 

 mammalian spermatozoa, it is seen that when in the immature, or 

 spermatid, condition, the potential spermatozoa contain all those parts, 

 (nucleus, cytoplasm, nebenkern and centrosomes) which are now becoming 

 associated with cell structure in general. To these are to be added 

 certain others, such as the chromatic body, the archosome, the cerco- 

 some, and the tail, which have apparently no representatives in other 

 than reproductive cells, while the three last only appear late, in the 

 history of these. The question naturally arises, what is the origin and 

 significance of these accessory bodies? In the first place it may be 

 said that their existence, in relation to the formation of the sperma- 

 tozoon, is very variable in different classes and orders of animals. 

 I am not aware that an accessory chromatic body has been found in 

 a lower class than the amphibia, and the same irregularity of appe- 

 arance is manifest with respect to them all. If, after a comparison 

 of the spermatogenetic process in widely separated groups of animals, 

 certain structures are seen to be common to them all, these may in 

 the first place be separated as of a higher order, than those which 

 are peculiar to each. 



The only structures which have any claim to this universality 

 are the nucleus, some form of cytoplasm, and the centrosomes, but 

 these are the constituents now becoming associated with all cell- 

 structure, whether reproductive or otherwise. They form an order over 

 whose existence the action of adaptive selection appears to have little 

 if any power. Considering the immense time and opportunity for 

 variation that the cells of so complex a type as the mammalian one 



