ORIGIN OF MONSTERS. II 427 



double monsters in our experiments can, accordingly, not serve 

 as an argument against the justification of our assumption of 

 osmotic pressure as an important factor underlying their 

 morphogenesis. 



The second component factor of blastolysis, chemical alter- 

 ation — is also largely inferred. However, this inference would 

 seem to be well justified, if the action of acetone, partly solvent 

 and partly as a precipitant of lecithine, is considered. Owing 

 to the effect of this action some groups of cells may be entirely 

 destroyed, while others may be only, more or less, chemically 

 modified* and thus lose much of their inherent capacity for 

 differentiation (inhibition) as well as of the power to resist the 

 action of osmotic pressure. 



Besides the two factors mentioned above attention may be 

 called to another factor which may play a contributory part to 

 the effect we term blastolysis insofar as the latter may be facili- 

 tated by it. This is the age of the egg, counting from the time 

 of its maturation. 



It has been found by several observers that the viability of 

 the eggs and their ability to develop in a typical manner de- 

 creases gradually after their maturation. 



Thus Hertwig ('92) noted that unfertilized frog eggs retained 

 (for some time after the animal had been killed) in the uterus 

 (on ice), showed with each consecutive day a greater tendency 

 to abnormal development, which in many of them resulted in 

 'spina bifida.' Like results have been obtained by him also 

 if female frogs were separated from males long enough for the 

 eggs to become over-mature. 



Conklin's ('97) observations on the eggs of Crepidula are very 

 striking and may therefore be best presented in his own words 

 (p. 30): 



. . . . when the adult Crepidulas are brought to the laboratory, 

 and kept in the best possible conditions, the percentage of these ab- 

 normalities increases, and when the egg capsules are removed from 

 the mantle cavity of the mother and. kept in dishes of sea-water, the 

 monstrosities increase to such an extent that after a few days not a 

 single normally developing egg or embryo can be found. 



