Some Observations on the Chromosome Vesicles in the Maturation ete. 103 
matin passes into the cytoplasm to contribute in part to the forma- 
tion of the sphere substance. 
5) No evidence of chromosome vesicles was found during the 
prophase of the first maturation as is the case in Haminea solitaria. 
6) During the »rest pause« between the first and second ma- 
turation, the chromosomes frequently have distinet vesicles.. There 
may be a single vesiele for all of the chromosomes or a single 
vesicle for each chromosome. All combinations between these two 
extremes occur. 
7) The chromosomes that pass into the polar cells likewise pos- 
sess vesicles which in some instances exhibit all of the structural 
features of a typical nucleus. 
85) The egg chromosomes enclosed in vesieles change while in 
this state until each vesicle has the appearance of a miniature 
nucleus. Before the metaphase of the second maturation, the several 
chromatie granules unite into a solid mass, the vesicle probably 
disappearing. 
9) The fact that the chromatin may normally exist in a liquid 
state during the prophase of the first maturation of Aaminea soli- 
taria and in the prophase of the second maturation of these Nudi- 
branchs strengthens the growing convietion that the theory of the 
qualitative division of the chromosomes is untenable. 
10) The growth and fate of the several parts of the centrosome 
are in close agreement with these same changes in the centrosome 
of Haminea solitaria. 
11) Fertilization takes place in the oviduct, the tail remaining 
outside. The sperm head becomes vesicular during its progress 
towards the animal pole and while it is undergoing this change one 
or more chromosome vesieles may be formed in connection, with the 
ehromatin derived from the sperm, which are similar to the egg 
ehromosome vesicles. These vesicles arise undoubtedly through the 
influence of the chromatin on the eytoplasm which faet suggests that 
the vesieles in these three Nudibranchs and those in Haminea soli- 
taria which arise in the nucleus are not identical. 
Zoologieal Laboratory, Syracuse University, 
May 1°, 1904. 
