258 A. RICHARDS. 



careful focusing gives in studying their structure is lost. Some 

 of the vesicles are more distinct than others, however, as is shown 

 in Fig. 10, where one of them stands out with especial clear- 

 ness. It may not be objected to these figures that they are 

 tangential sections and that the vesicles really fuse in the center 

 of the nucleus, for many of these nuclei extend through three 

 sections and in each of the sections the same conditions are seen ; 

 if this condition were due merely to the tangential cut of the 

 section the second of a series of three would not show the vesicles 

 separately as it actually does. 



Reconstruction consists in the further swelling up and rounding 

 out of the anaphase vesicles and their close approximation to 

 each other in the telophase. In the completely reconstructed 

 nucleus the approximation of the vesicles is very close, so that 

 they are no longer to be recognized as separated bodies. Yet 

 the appearances do not indicate any actual fusion. One sees 

 a nucleus consisting of vesicles so closely applied to each other 

 that they conform in shape each to the other, and there are 

 left no spaces between them. The inner boundaries are less 

 sharp than the nuclear membrane, but even the nuclei which 

 are only lightly stained show areas marked off from each other 

 which represent the tightly packed vesicles. In every resting 

 nucleus, whether radiated or not, which I have studied these 

 areas can be made out. Fig. 15 represents a fairly typical case, 

 although in other nuclei the vescular structure is even more 

 apparent. That these vesicular areas do not represent simply a 

 delay in the complete fusion can be seen by referring to Fig. 22 

 where their walls are still distinct, although the new chrom- 

 osomes for the next division have been formed. 



The resting condition of the nuclear vesicles is shown in Figs. 

 13, 14 and 15. The first two of these are from eggs before the 

 first cleavage division; until they were found the writer did not 

 feel sure that the vesicular condition represents more than a 

 delay in the fusion and that the final result might be such as 

 Moenkhaus has described. Since in these cases there had been 

 no preceding division, however, and since it does not seem that 

 the unfused condition would persist so long as from the matura- 

 tion division and over the fusion of the pronuclei if the parts do 



