WILCOX: SPERMATOGENESIS. 17 



division of the spermatogonia and tho first division of the spermatocytes. 



He maintains that the first division of the spermatocytes is a reduction 



division and the second an equation division. His number relationships 



for the chromosomes are hence the following : — 



Spermatogonia 24 



Spermatocytes, 1st order, 12 bivalent rings ... 24 



Spermatocytes, 2d order 12 



Spermatids 12 



The only reference by Henking to rings of the value of four chromo- 

 somes is in this sentence : " Ich mache besonders auf die mit vier Ver- 

 dickungen versehenen Ringe 1 und 2 in Fig. 20 aufmerksam." The 

 two rings to which Henking refers contain each four nearly spherical 

 chromosomes, and these, I believe, are the only instances in which 

 Henking recognized the real value of chromatic rings. Each ring con- 

 tains four chromatic elements, each half-ring two elements, and since 

 these two elements are separated from each other at the second sper- 

 matocyte division, this, contrary to his conclusion, is just as truly a 

 reduction division as is the first. But Henking objects to this in- 

 terpretation : " Es findet hier also keine Reduction statt, sondern eine 

 gewohnliciie Aequationstheilung, welche jedoch hier schon von fernher 

 vorbereitet war." But if each ring has the value of four, not simply 

 two, chromosomes, the same argument could be applied to the first as 

 well as the second spermatocyte division, as Brauer ('93) has already 

 done. The soundness of these objections will be considered in connec- 

 tion with Brauer's paper. 



Hacker ('92* and '93) has seen ring formation and Vierergruppen 

 in the oogenesis of several marine Copepods. In the genera, Euchseta, 

 Calanus, Cyclops, Diaptomus, Canthocamptus, and Heterocope, he main- 

 tains ihat " zwischen die letzte Theilung der Ureizellen und die erste 

 Theilung der Reifungsphase ist kein feinfadiges Ruhestadium des 

 Kernes (Keimblaschenstadium) eingeschaltet." In the eggs of some 

 females this resting stage is passed over, in others not. In those females 

 in which the resting stage in oogenesis is twice omitted, i. e. both before 

 and after the formation of the first polar globule, Hacker ('92) sug- 

 gests, as a motive for the omission of the first resting stage, that in this 

 way " im Mikrokosmus des regenerativen Lebens eine weitgehende 

 Anpassungsfahigkeit zur Geltung gelangt." This omission, then, is a 

 biological adaptation. The maturation of the egg is thus brought about 

 sooner. This explanation is mentioned, because it has a direct bearing 

 upon any interpretation of the rings, as will soon be seen. Hacker 



VOL. XXVII. — NO. 1. 2 



