2/8 



BASlll'OKl) UEAN. 



which by hardening appear as edges of deep fissures. So deeply 

 indeed do these pass into the yolk that the writer was able 

 by means of needles to remove a yolk mass - - that lying in the 

 middle of the lower half of the figure --almost entire. This 

 mass, however, broke down in the process of further hardening, 

 and no sections of it could be prepared. In later stages (Figs. 

 5 and 17) fragmentation continues still further. The embryo 

 with its circumcrescent blastoderm is now attached to a relatively 

 small portion of the yolk ; the remainder is broken up into 

 masses, big and little, and in the living egg the smallest are found 

 dissolving into a pasty or creamy liquid, which at first sight is apt 

 to hide the embryo and lead the observer to believe that the egg 

 is dead and addled --an impression he soon loses when he dis- 



FIG. 13 14 15 1 6 



FIGS. 13-17. Eggs showing the progressive cleavage of the yolk mass. Ina 

 blastula (13) a conspicuous fissure is noted between the points * and *. In an early 

 gastrula (14) a fissure extends hindward from near the rim of the blastoderm. In a 

 'ater stage (15) a progressive fissuring of the yolk mass is seen, anteriorly and poste- 

 riorly, and notably in the ventral region (16). In the stage of Fig. 17 the entire 

 yolk mass has undergone division, the blastoderm appropriating a single mass (slightly 

 shaded -in the figure). 



covers a moving embryo and finds that the fluid is odorless. In 

 ascertaining this the writer may mention, parenthetically, that he 

 was on the point of losing one of his most valuable stages. An 

 egg-case was brought in which had been taken by accident, hav- 

 ing become entangled in a trawl line ; it was light in weight and 

 its general appearance of wear and tear indicated that it was an 

 empty shell ; it was opened, however, and showed a milky fluid 

 which suggested, by analogy of shark eggs, an unpleasantly late 

 stage in decomposition. But as the writer began to pour out 

 the contents of the case carelessly, he saw to his surprise a 



