Katharine Foot and E. C. Strobell 209 



the male and female pronucleus. In the vesicles formed at the telophase 

 of the second maturation spindle " a small dense homogeneous nucleolus 

 is first seen in close proximity to each chromosome (Foot and Strobell, 

 'oo). These increase in size by groAvth and by irregular and inconstant 

 fusing with one another. Thus in the resting female pronucleus we 

 find nucleoli, Avhich like the accessory nucleoli are inconstant in size and 

 number, and this inconstancy is true also for the nucleoli of the male 

 pronucleus. One or several of these may persist until the metaphase of 

 the first cleavage spindle and like the accessory nucleoli may be in the 

 spindle or in the surrounding cytoplasm. These, like the accessory 

 nucleoli, are relatively dense homogeneous structures as compared with 

 the large nucleolus of the oocyte first order, and these points of agree- 

 ment suggest the possibility of a closer relationship — may not the acces- 

 sory nucleoli of the germinal vesicle arise in connection with the chromo- 

 somes of the first spindle before instead of after their division? If, as 

 held by a number of investigators, the chromosomes of one divi-jion are in 

 some manner related to the nucleolar substance of the following rest 

 stage, may not this be established at an earlier period and the accessory 

 nucleoli of the germinal vesicle be a precocious appearance of the nucleoli 

 which are so conspicuously absent between the first and second spindles ? — 

 the processes involved in the rest stage occurring before instead of after 

 the first division, the origin and growth of the accessory nucleolus being 

 part of them. The second division precociously foreshadowed in the four 

 part chromosomes of the germinal vesicle suggests a precedent for this 

 interpretation. 



If our interpretation of the accessory nucleolus is correct, a like struc- 

 ture should be present in spermatocytes, and there should be two nucleoli 

 in the spermatocyte first order in all cases where a resting stage is omitted 

 between the first and second division. Such a condition is figured by 

 Vom Eath, '92, in Gryllotalpha. His Figs. 10 and 11 show two nucleoli 

 in the spermatocyte first order at the spireme stage in which they are 

 conspicuous also in AUolohopliora, and it is significant and interesting 

 that the two nucleoli in the spermatocyte are nearly equal in size. See 

 also Schreiners, '04, Figs. 23 and 24. 



"The transformation of the chromosomes into vesicles at the telophase of 

 the second maturation spindle was first seen in RJiynchelmis and described 

 and figured by Vejdovsky in 1887. Our Photo. 32 shows one of these vesicles 

 in a second maturation spindle and indicates that their formation is not 

 necessarily dependent upon a definite form or position of the chromosomes, 

 as this vesicle is formed before the telophase, and the chromosomes have not 

 assumed the shape they usually show, when at the lower pole of the spindle, 

 prior to the formation of the vesicles (Foot & Strobell, '00, Photo. 24). 



