DEPARTMENT OF MARINE BIOLOGY. 241 



various duplicities (quite a number of which were recorded this summer), 

 amorphous embryos, and other general deformities. 



However, besides the increase in osmotic pressure, there is another factor, 

 viz, toxicity of the medium, which is responsible for blastolysis. The solu- 

 tions of the organic acids employed in these experiments seem to have a solvent 

 effect on the egg. When the eggs are transferred from these solutions to pure 

 sea-water they swell at first and then some dissolved parts of their substance 

 are seen to pass out of them into the water. This can be observed in a striking 

 manner, particularly in eggs which have been treated with butyric acid. In 

 some of them, which eventually give rise to extremely deformed embryos, the 

 yolk-sacs are reduced to a very small size, owing to this loss of substance. 



The substances which pass out of the egg after transfer to pure sea-water 

 form a sediment on the bottom of the dish, which is slimy in butyric-acid 

 experiments and of a granular consistency in acetone experiments. It is 

 planned to collect these sediments during the next season, and by means of 

 chemical analysis to thus ascertain the chemical effects which these acids 

 produce on the egg. 



There are, then, two processes involved in the blastolytic action. For the 

 sake of convenience I shall term the supposedly solvent action of the sub- 

 stances employed — which manifests itself in the destruction of a certain area — 

 the toxic blastolysis, while the fragmentation due to osmotic pressure will 

 be referred to as osmotic blastolysis. 



In most monsters which are produced by the influence of butyric acid and 

 acetone solutions both factors play an important part, the toxic blastolysis 

 being followed on transfer to pure sea-water by osmotic blastolysis. In 

 embryos, however, whose defects are mainly restricted to the eyes, the effect 

 is largely due to toxic blastolysis, for there is in such cases usually only a 

 slight indication of dissociation by osmotic pressure. 



Similar effects can also be produced by lowering the temperature of the eggs' 

 environment. Loeb^ has recently shown that if Fundulus eggs be kept on 

 ice for certain periods of their development some of them will develop into 

 monsters. I have repeated these experiments this summer and have obtained 

 the same results, even with a much higher temperature than the one used 

 by Loeb. However, in this case, too, I was able to observe escape of substance 

 from the egg, which resulted in a striking reduction of the volume of the yolk 

 in eggs which had developed in a monstrous manner. This escape of substance 

 seems largely due to shrinkage caused by the low temperature. Thus some 

 monsters produced by the effect of low temperature on the developing egg may 

 be due to loss of the egg's substance, while the ophthalmic monsters are probably 

 due mainly to the injurious effects of the lower temperature. As I have 

 pointed out elsewhere, the ophthalmic defects in my chemical experiments 

 seem to be due to toxic blastolysis, by which the potential ophthahnoblastic 

 material is primarily affected. This part of the egg is evidently characterized 

 by a high degree of sensitivity, and is most rapidly altered in the chemical 

 experiment as well as in the temperature experiment. 



The rudimentary development of the blood vascular system in eggs so 

 treated is, contrary to Loeb's assumption, in no causal connection with the 

 ophthalmic defects. It is well known that in the normal development the 

 optic vesicles are laid down long before any blood-vessels are formed. 



^Loeb, J., The blindness of the cave fauna and the artificial production of blind fish embryos by- 

 heterogeneous hybridization and by low temperatures. Biol. Bulletin, vol. XXIX, No. 1, 1915. 



