HISTORY OF CHROMOSOMAL VESICLES IN FUNDULUS. 269 



(8) The oxychromatin spherules grow smaller and are dissolved 

 in the nuclear sap while others are arranged in series on the linin 

 threads into which they are formed; these threads with attached 

 spherules form the spindle fibers." Thus the relation of the 

 old vesicle to the new chromosome is followed out. 



Evidently from this description there is a close parallel between 

 the behavior of the chromosomes of Crepidula and those of 

 Fundulus eggs. Much of this summary will fit, word for word, 

 the conditions which have been delineated in the preceding 

 pages, although in Fundulus the vesicles do not fuse in the resting 

 stage. 



Conklin points out the fact that "such vesicles are found 

 generally, if not uniformly, in the early divisions of the ova 

 though they are not usually found in other mitoses." He 

 attributes this to the difference in size and rapidity of division 

 of the blastomeres as compared with tissue cells, and concludes 

 "that in the large cells where divisions succeed each other at 

 short intervals, the chromosomes begin the growth characteristic 

 of the daughter nuclei, i. e., the absorption of substances from 

 the cell body, before they have fused together, whereas in small 

 cells or cells which divide only at long intervals the chromosomes 

 fuse before the absorption of achromatic material begins." With 

 this conclusion the facts as found in Fundulus in general are in 

 accord. 



In both kinds of eggs also the growth stages of the daughter 

 nuclei are quite alike. In Crepidula "after the fusion of the 

 chromosomal vesicles to form the daughter nuclei, the latter 

 continue to absorb achromatic material, growing larger and 

 larger until the prophase of the next division. A part at least 

 of the achromatic material absorbed is derived from the sphere 

 which in turn contains interfilar substance of the spindle and 

 aster. This recalls the conclusions of O. Hertwig in which he 

 points out that in the formation of the daughter nucleus the 

 chromosomes absorb ' Kernsaf t ' and become vesicular, the proc- 

 ess being the reverse of what occurs in the beginning of division 

 where ' Kernsaf t' is set free into the cell body. A similar view 

 was held by Butschli . . . ." 



The most important point of difference between Conklin's 



