338 bulletin: museum of comparative zoology. 



spherical outline and becomes oval (Fig. 110), a fact which it is neces- 

 sary to bear in mind when comparing the sizes of cells viewed in differ- 

 ent directions (compare Figs. 110 and 112) ; at the same time, as in 

 other cell generations, the karyoplasm becomes less and less dense, and 

 finally (Fig. 112) disappears altogether, leaving the nucleus in the ap- 

 parently empty condition with which we are familiar in other mitoses in 

 Gonionemus. 



Hand in hand with these changes the net continues to thicken, while 

 the karyosomes increase in size and numbers, many of them now lying 

 (Fig. 110) along the courses of the strands, instead of only at their 

 nodes. This process continues, and the chromatin masses become more 

 and more ci'owded until finally (Figs. 113, 114) the net consists of a 

 considerable number of thickened beaded segments connected with the 

 nucleolus and with one another by linin strands. This is essentially 

 the condition presented by the entoderm cells at a corresponding stage. 

 The nucleolar shell now separates into several distinct chromatin masses 

 (Fig. 113), which seem to migrate outward along the linin strands at 

 whose points of origin they were situated, and the denuded plasmosome 

 is now visible lying between them (Fig. 113). This latter structure 

 must shortly break down or be absorbed, for it is absent in all later 

 stages. 



At various periods in the prophase, often even before the disintegra- 

 tion of the nucleolus, contraction phases similar to those already de- 

 scribed among the male germ cells (page 314) are found, and here they 

 usually take the form of extreme condensation, as is shown in the cell 

 represented in Figure 111. The occurrence of such appearances has 

 already been discussed at length (see page 315). In the present case the 

 chromosomes appear, as would be expected, in the full somatic number ; 

 they therefore cannot be connected with any process of synapsis, but 

 are purely the result of the action of reagents. The later prophase is 

 very similar to that of the entoderm cells. After the final disappear- 

 ance of the plasmosome the cells present the appearance shown in Figure 

 114. The entire chromatic substance of the nucleus is now condensed 

 into a considerable number of " beaded segments," which, being still 

 connected by achromatic strands, preserve the net-like condition. I 

 have never seen any indications that they become metamorphosed into 

 a single continuous spireme thread. I believe, however, that we must 

 regard this stage as homologous with the segmented spireme, since there 

 appears to be no further segmentation of the chromatic strands. The 

 nuclear membrane now breaks down, and the nuclear space is invaded 



