356 LOUIS 1. DUBLIN. 



chromatin appears in two masses ; one localized at the anterior, 

 the other at the posterior end of the now elongated sperm head, 

 there being a non-staining middle space between (Fig. 11). On 

 such a condition as this one might extend to this post-maturation 

 stage the same interpretation that was criticized above. 



Indeed Hacker would so conclude. In his '02 work, re- 

 ferred to above, this author is quite ready to interpret 

 the presence of two nucleoli in the matured sperm head 

 FIG. ii. as an indication of the persistent autonomy of the paren- 

 tal chromatin halves, even until this period. The only uncer- 

 tainty, as he admits, in the Copepods under consideration (Diap- 

 tomns and Heterocopc] being the presence of three or four nucleoli ; 

 nor are these placed at two opposite points of the nucleus as his 

 hypothesis of gonomery demands. 



In the matured egg, however, he finds absolutely no difficulty 

 in accepting this conclusion. Speaking of the chromosomes at the 

 beginning of the second maturation division, he states, p. 343 : 

 "Die 12 neuformirten bivalenten Elemente . . . werden durch 

 den Reduktionsakt auf der zweiten Richtungskorper und Eizelle 

 verteilt und letzterer enthalt demnach 6 Mischlinge, welche sich 

 je aus einer vaterlichen und mutterlichen, oder, da die reife Eizelle 

 bereits eine neue Generation reprasentiert, besser gesagt, aus 

 einer groszvaterlichen und groszmutterlichen Halfte zusammen- 

 setzen." To understand fully what this post-maturation go- 

 nomery of Hacker involves, it is necessary to review in more 

 detail the processes by which it is attained. In a late prophase 

 of the first maturation mitosis, the twenty-four chromosomes (the 

 somatic number) appear in two rows of six pairs each ; the paired 

 bivalent chromosomes having arisen through the union end to 

 end of single chromosomes of the same parental side. Thus, 

 the twelve paternal chromosomes, a, b, c, d, c, f, g, //, /, /, /', /, 

 are arranged ab, cd, ef, gli, if, kl, while correspondingly those 

 of the maternal side as no, pq, rs, tit, vw, xy. Each of the 

 pairs then splits longitudinally forming twelve tetrads, six com- 

 pletely paternal and six completely maternal. The first matur- 

 ation which is equational reduces the tetrads to dyads leaving in 

 the egg twelve bivalent chromosomes, six from each parental 

 side. Now ensues a second synapsis between pairs, this time of 



