228 MICHAEL F. GUVER. 



Fig. 1 1 represents a prophasc of the secondary rather than an ana- 

 phase of the primary division although I am inclined to think it is 

 the latter. If such simple divisions do take place, however, they 

 are certainly scarce in the material which I have examined so far. 



From the foregoing evidence it is manifest that there are in all 

 two distinct groups of spermatids equal in number; namely, 

 those which have received five and those which have received 

 seven chromosomes. These chromosomes soon lose their visible 

 identity and the spermatids are apparently all alike except for the 

 significant fact that approximately half of them, in such prepara- 

 tions as have been stained by the iron-haematoxylin method and 

 then all but entirely decolorized show two chromatin nucleoli. 

 It would seem probable that these nucleoli stand in direct genetic 

 continuity with the two eccentric chromosomes seen in the sper- 

 matogonia and the two chromatin nucleoli and the accessory 

 chromosomes of the spermatocytes. Fig. 18 represents two con- 

 tiguous spermatids, one of which shows no nucleoli, the other, two. 

 Comparison with Fig. 19 shows the relative conditions of size be- 

 tween the nucleoli of the spermatid and those of a primary sper- 

 matocyte. 



As to the meaning of the second conjugation there seems to be 

 at present no clew. I have commented on it briefly in a former 

 paper ('090, p. 509). It is not peculiar to man for I have observed 

 it also in the pigeon ('02, '03), the guinea ('oga) and the rooster 

 ('096). Undoubtedly Bardeleben ('97, '98) still earlier saw the 

 same phenomenon in man, for although my results do not agree 

 numerically with his count of sixteen, eight and four respectively, 

 evidently, from the relative proportions in his counts, he had come 

 upon this second curious numerical reduction. 



Assuming that the respective ehromosomes are more or less 

 qualitatively differentiated, such a numerical reduction, however, 

 by no means necessarily implies that there has also been a second 

 qualitative reduction. Aside from the improbability of such a 

 reduction, the general appearance of the divided chromosomes 

 would not warrant this interpretation; for instead of the elongated 

 univalent type as seen in the spermatogonia or in anaphases <>t tin; 

 divisions of spermatocytes of the first order, the daughter chromo- 

 somes here retain the rounded appearance and increased size that 



