SECT. 6] 



OF THE EMBRYO 



909 



.E40 



was related by Bialascewicz to the presence of the blastopore. The 

 slight diminution in absolute volume between the 50th and 11 8th 

 hours is reflected on the speed curve by a big drop, but after that the 

 curve rises with only minor variations. Both Davenport and Schaper 

 noted an increased growth-rate in the frog larva after hatching, so 

 that the results of all the workers 

 on the frog embryo are in agree- 

 ment with those of all the workers 

 on the trout. The whole mass of 

 data shows clearly an absorption 

 of water diluting the yolk as it is 

 transformed into the tissues of 

 the embryo. ^20 



Bialascewicz also investigated ^ 

 the part played by the jelly of | 

 the frog's egg after hatching as a s 

 source of solid and water for the ^ 

 embryos. Frog larvae are nearly - 

 always to be seen hanging on to 

 the jelly with their suckers after 

 having hatched, and Bialasce- ^^' ^'^'^' 



wicz rightly thought it not improbable that the jelly might contribute 

 something to the larvae. Measurements certainly supported this; 

 thus the average weights of larvae he found to be as follows : 



100 200 300 



Hours from fertilisation 



Weight in milligrams 



8 days 

 26 days (in distilled water) ... 

 26 days (in distilled water but plus the jellies) 



Wet 



9-52 

 25-24 

 84-46 



Dry 



I -08 



4-22 



This was a striking demonstration of the absorption of water. In the 

 second instance much water had been absorbed, but the dry sub- 

 stance was the same in amount, or rather slightly reduced owing to 

 combustion of yolk, whereas if the jellies were present the dry sub- 

 stance was much increased as well as the water. The loss of dry 

 substance from the larvae was also found by Bialascewicz for the 

 early stages; thus, between the ist and the 4th day, about 5 per cent, 

 of the dry weight was lost. He measured the effect of temperature on 

 the increase in volume of frog's eggs at different stages, and came to 

 the conclusion that temperature had no effect on the amount of water 



