94 CHARLES V. MORRILL. 



all of the first polar metaphase (Fig. 5, e, f, g and //). 10 Two of 

 these U> and /) are complete, showing se\vn bivalents. The idio- 

 chromosome bivalent can be positively identified by its relatively 

 enormous size, having been formed, no doubt, by the synapsis 

 of the two largest chromosomes (idiochromosomes) of the oogonia 

 It does not in any way resemble a nucleolus. The bivalent next 

 in size, corresponding to the two next largest chromosomes of the 

 oogonia, can also be identified. Indeed the bivalents as a whole 

 show the same relative size differences as the chromosome pairs 

 in the oogonia. The w-chromosome bivalent is the smallest but 

 only slightly smaller than the next in size. In Fig. 5, /, three 

 chromosomes of intermediate size are seen in face view; two of 

 these exhibit a quadripartite form, clearly indicating their bivalent 

 nature. Fig. 5, g, is a side view of an incomplete metaphase, 

 drawn from two sections, showing six of the seven chromosomes, 

 and Fig. 5, h, shows a metaphase, side view with only five chromo- 

 somes, again taken from two sections. In both of these figures 

 the idiochromosome bivalent can be readily identified by its n/e 

 and the plane of the second division is clearly indicated in all the 

 bivalents. While the further processes of maturation were not 

 followed, it may be inferred, on the analogy of Archimeriis, that 

 in the anaphase of the first division the seven tetrads divide into 

 two groups of dyads and the inner group of these separate in 

 the second division into two groups of monads; the inner group 

 of these last named, seven in number, enter into the formation of 

 the female pronucleus, which is thus similar in chromatin-content 

 to a spermatozoon bearing the idiochromosome. 



4. Conclusions Regarding Oo genesis. 



The results on maturation are somewhat meagre it is true but 

 perfectly clear as far as they go, and point to the conclusion that, 

 unlike the spermatozoa, all (he mature eggs are of OIK- kind with 

 respect to their chromatin-content, as has been assumed. Tin- 

 female pronucleus contains a reduced group of chromosomes 

 similar in size and number to that carried by a "female-pro- 



l Thc excessive size of the chromosomes in these figures, especially those of g 

 and h. is probably due to the peculiar action of the fixative (see footnote 8, on 

 page 89). 



