Some Pdints in the Spfiinatdt^enesis of Mammalia. , J 51 



From these facts, it would appear hardly contestable that the 

 extra nuclear chromatic mass, seen in the spermatog-enesis of many 

 mammals, is produced by the direct transference of small nuclear i^-a- 

 nules to the cell body; but the extreme variability of this chromatic 

 body in a ^roup so highly organized as the mammalia, suggests that 

 it cannot be in any way essential to the formation of the sexual 

 elements, and that it probably serves some adaptive purpose. 



For a short time the spermatids retain, unchanged, the characters 

 just described, i. e. they contain a pale de-chromatised nucleus, a chro- 

 matic body and an archoplasm. But as soon as the disturbances 

 l)roduced during mitosis (which, for the time being, obscui'e the cen- 

 trosomes in a thick granulation) have subsided, bodies having all the 

 appearance of resting centrosomes reappear beside the nucleus ^) 

 (Figs. 15, 16, 21, 23) and for a short time continue to grow more 

 distinct. 



[ have so far been unable to detect these bodies with certainty 

 at the same stage only in mammals other than the rat. In dogs, the 

 spermatids, at a period obviously corresponding to the one which I 

 have just described, show numerous groups of three, foui\ or even five 

 nuclei, in the same irregular mass of cytoplasm. These multi-nucleate 



^) The occiuTBUce of this chromatic trausfiguration in the spermatids will be 

 of considerable theoretical interest to many, is it is just the method by which 

 Weismann supposed the nucleus to transmit its successive „ids" of germplasm, to 

 work their corresponding metamorphosis in the cell. And, to say the least, it is 

 curious that the exodus occurs just at the beginning of the direct metamorphosis 

 of the cells into spermatozoa. 



The more closely we look however, the less certain does it appear that this 

 change is wrought by the presence of the microsomata or „ids" in the cell at large. 

 For example, there is every reason to believe that the lengthening out ot the body 

 of the spermatid (one of the most marked features of its conversion) is primarily 

 due to increasing pressure in the tubule. So also, the disintegration of the great 

 mass of cytoplasm, which, together with the Residual Archoplasm, constitutes the 

 residual corpuscle, gives all the appearance of being brought about by insivfficieucy 

 of nutrition, in virtue of its position. Again, there is much to support the view 

 that the more or less symmetrical arrangement of the centrosomes. chromatic bodies, 

 and residual archoplasm, about the axial thread of the tail, is also an outcome of 

 lateral pressure ; and there is nothing to show that the coalesced microsomata of the 

 chromatic body influence these in any way. In fact, it would be quite as legiti- 

 mate to turn the tables, and suppose that the residual archoplasm may itself in- 

 duce the symmetrical arrangement of the chromatic bodies about the axis of the tail. 



