No. I.] CH^TOPTERUS PERGAMENTACEUS. 31 5 



represents a somewhat later stage of the egg, viewed in hori- 

 zontal section. It, therefore, shows the four centrosomes, but 

 not the lobe. The latter is represented in vertical section at 

 still a later stage in Fig. 8. 



When the chromosomes have reached a position near the 

 poles of the spindle, each of them swells up to form a vesicle in 

 which at first two distinct rows of granules may be seen, 

 recalling Victor Herla's ''division secondaire" in the chromo- 

 somes of Ascaris megaloccphala. Later each chromosome ex- 

 actly resembles a miniature nucleus. They are separated from 

 one another, and rays from the astrosphere may sometimes be 

 seen in the interspaces. The two centrosomes at either pole 

 have by this time traveled some distance apart. The rays 

 are exceedingly clear, and extend to the periphery in all 

 directions (Figs. 7 and 8.) 



A few rays may be traced into the before-mentioned lobe at 

 the vegetative pole. The lobe has now begun to constrict at 

 its base (Fig. 8). 



The nuclear vesicles swell still more, press against one 

 another laterally, and constitute in each cell a disc-shaped 

 nucleus, which later becomes spherical. Whether the vesicles 

 actually fuse or not, I do not know. 



The lobe spoken of above becomes completely constricted off 

 and lost without leaving a scar upon the egg. It is always 

 borne upon the larger cell and is composed almost exclusively 

 of yolk. It is covered by the egg-membrane. Fig. 9 is from 

 a camera drawing of an egg mounted whole, with the lobe 

 almost completely pinched off. The lobe may always be seen 

 connected with the egg by a more or less narrow neck during 

 the reconstitution of the nuclei, and it always completely 

 disappears by the time the nuclei have become spherical 

 (Fig. 10). 



It is obvious that the foregoing account of the behavior of 

 the centrosomes is entirely unlike that of the " quadrille of the 

 centrosomes " described by Fol, Guignard, and Conklin. I am 

 convinced that in Chcetoptcriis there is no fusion of the male 

 and female centrosomes, and I believe that the female centro- 

 somes degenerate after the polar globules have been expelled. 



