276 



INEZ WHIPPLE WILDER. 



stage D is reached (n days, at the latest, from the time of 

 hatching), practically all external evidence of the presence of 

 yolk has disappeared, though dissection and sectioning both 

 demonstrate the presence of an abundance of yolk granules in 

 the walls of the intestine. With this reduction of the yolk 

 protuberance, the medial edges of the rectus abdominalis muscles, 

 widely separated at the time of hatching, gradually approach 

 each other and finally meet in the linea alba. 



The changes in the shape and appearance of the tail are 

 noteworthy. The tail becomes longer, so that from being at 



df 



a 



1) 



FIG. 7. Cross sections, at approximately the same level, cf the tails of (a) a 

 newly hatched larva, terrestrial stage A, and (6) an aquatic larva, showing the 

 difference in proportions, and the development of the dorsal fin (df). For the 

 level of the sections cf. Plate I., Figs, i and 10, Drawn with Abbe camera. X 60. 



the time of hatching only 41 per cent, of the total body length, by 

 the time the larvae have reached the water and become typical 

 aquatic larvae (stage F, averaging only 15 or 16 days from the 

 time of hatching) this same measurement is found to be over 47 

 per cent, of the total body length. With the increase in length of 



