IN ONTOGENESIS 



787 



SECT. 5] 



mann's results, but, although his were regular, they never exceeded 

 plus or minus 5 per cent., while Adolph's were of the order of 30 per 

 cent. As volume decreased in some dilute salt solutions, Adolph 

 concluded that the egg-membranes were not completely permeable 

 to sodium chloride. The next stage investigated was the yolk-plug 

 stage. "The results were unexpectedly irregular and allowed of no 



2 3 



Time in hoars 



Fig. 180. Unfertilised eggs. A, Loss in volume; B, gain in volume. 



precise definition of the relation between volume and concentration. 

 Possibly the egg is comparatively semipermeable in the dilute 

 solutions, but in stronger ones is made completely permeable to 

 solutes." This would explain the relationships seen in Figs. 180, 

 i8i and 182, taken from Adolph's paper. After hatching, the 

 response became more regular, and predictions of the results 

 could be made. Adolph concluded that from the unfertilised tgg 

 up to metamorphosis no marked changes in regulatory activity oc- 

 curred in Rana pipiens. The only definite diflference was that the eggs 

 and embryos lost relatively less in volume when immersed in strong 



