CHROMATIN — DEVELOPMENT AND HEREDITY 231 



rods complete their division first. That in figures of later ana- 

 phases the shorter chromosomes had long escaped observation 

 is not surprising in view of the compact arrangement of the 

 daughter plates already emphasized. 



Ctenolahrus adspersus 9 X Ctenolabrus adspersus cf 



The Ctenolabrus egg is the smallest of the pelagic eggs used. 

 Its transparency, which permits the progress of segmentation to 

 be followed easily, and the rapidity with which -it develops 

 make it a favorite object for embryological study. 



The fish are small and quite easily handled and mature females 

 yield a large number of eggs, which is an added advantage. The 

 eggs are very susceptible to adverse conditions, and numbers in 

 every lot were evidently injured during the process of stripping 

 and addition of the sperm. The eggs were stripped into finger 

 bowls containing a slight quantity of sea-water, the sperm added 

 and stirred thoroughly among the eggs. After one or two 

 minutes more sea-water was added. The eggs surviving this 

 manipulation were skimmed off into bowls of fresh sea-water. 

 The first cleavage occurs about forty to fifty minutes after 

 fertilization, but no careful observations were made on the cleav- 

 age rate. 



Reference has been made in the introductory section of this 

 paper to the nature of the chromosomes in the Ctenolabrus egg 

 fertilized by spermatozoa of its own species. The elongated 

 rod-like form of these bodies is evident. They have little re- 

 semblance to the metaphase chromosome in figure 9 of Miss 

 Morris's paper. Figure 7 shows, in three sections, an early 

 anaphase of the fourth cleavage A slight twisting of the spindle 

 fibers has resulted in obscuring certain elements while leaving 

 others well exposed to view. Straight rods, hooks, and two 

 thicker bodies, which I interpret as V-shaped chromosomes, 

 stand out clearly. Comparison with figure 4 shows that the 

 longest rods of Ctenolabrus approximate in length the short- 

 est rods of Fundulus. The spindle is also broader and the in- 

 dividual chromosomes more widely separated, hence the band- 



