270 A. RICHARDS. 



observations and mine is the matter of ultimate fusion of the 

 chromosomal vesicles in the resting stage, and the formation of 

 the new 'chromosome in the vesicle. In Fundulus there can be 

 no doubt that a direct continuity exists between vesicle and 

 prophase chromosome and that the vesicles do not fuse during 

 the rest period. One is compelled to suspect that Crepidula 

 offers less favorable opportunity for the study of this particular 

 detail than Fundulus. Conklin himself believed that there is a 

 real independence of the vesicles although they appeared to fuse, 

 and it may be inferred from the following paragraph that he 

 expected their persistent identity throughout the resting nucleus 

 to be proven in time. The observations on Fundulus may be 

 taken as a confirmation of his view expressed in 1902. 



"It sometimes happens, especially in eggs in which more than 

 the normal number of centrosomes and asters are present, that 

 some or all of the chromosomal vesicles do not fuse but remain 

 distinct through the whole resting period. In such cases each 

 of the vesicles behaves like a minature nucleus, absorbing the 

 achromatic material and forming a network of chromatin either 

 within the vesicle or on its walls. In this growth and differentia- 

 tion the vesicle keeps pace, step by step, with the normal nucleus, 

 so that one must regard the resting nucleus as virtually com- 

 posed of vesicles, though their union may be so intimate as to 

 hide this structure. The resting nucleus is not, therefore, a 

 single structure any more than is the nuclear plate. It is com- 

 posed of units each of which so far as known, has the properties 

 of the entire nucleus, and the union of these vesicles into a single 

 one may be considered as a secondary character. It is altogether 

 probable that the chromosomes and hence the chromosomal vesi- 

 cles, preserve their identity throughout the resting nucleus." 



Moenkhaus also was unable to see in the nuclei of the resting 

 cells evidences of separate chromosomes, yet he too, believed that 

 the substance of each chromosome forms a persisting unit. We 

 may expect then that the next step in the proof of chromosome 

 continuity and persistence is the recognition of structures in the 

 resting nuclei which can be homologized with the chromosomes 

 of the metaphase plate. This I believe is accomplished in the 

 fish eggs of my experiments. Moenkhaus states the case as 



