TELEOST OVUM. 53 



sponsible for pathological development. Thus the etiology of 

 defective or monstrous development would be traced to the 

 pathological metabolism of the mother or possibly even of the 

 father. For, as Bardeen^ has shown, a normal, healthy ovum of 

 the toad, if fertilized with sperm which had been injured by 

 exposure to the action of X-rays, will give rise to a deformed 

 embryo. 



With this idea in mind the writer conducted during the summer 

 of 1914 experiments on eggs of Fundulus heteroclitus. The eggs 

 of this fish are easily obtained at Woods Hole and are excellent 

 material for experimentation. The investigations on the fish 

 eggs are of a preliminary character, and were undertaken to 

 ascertain the influence of some toxic substances occurring in 

 pathological metabolism on the developing egg. 



The number of these substances being rather large while the 

 spawning season is limited to a few weeks, it was impossible to 

 try more than a few of the chemicals. Urea, butyric acid, lactic 

 acid, sodium glycocholate, acetone and ammonium hydroxide 

 were tried as to their effect on the development of fertilized eggs. 

 Definite results were so far obtained only with butyric acid and 

 acetone. 



Ten c.c. of a 1/12-1/14 molecular solution in 50 c.c. of sea water 

 was found to give the greatest number of monsters when butyric 

 acid was used. The eggs were submitted to the action of this 

 solution for 20 hours after they had reached the eight-cell or 

 sixteen-cell stage, i. e., 3 to 3>^ hours after fertilization. While 

 under this procedure numerous monstrosities were at first ob- 

 tained, the method failed almost completely in later experiments. 

 I therefore employed developing eggs in the first stages of division 

 (2- and 4-cell stages) when many monstrosities were produced 

 even after a sojourn of thirty hours in the butyric acid solution. 

 But it seems to me that the reason why the method failed with 

 the eggs in more advanced cleavage stages was that the time of 

 exposure was too long, as very many eggs were dead by the 

 end of that treatment, and that with an exposure of 10 or 15 hours 

 better results would have been obtained. 



There is, however, as important difference in the effect which 



1 Bardeen, C. R., Jour, of Experimental ZooL, 1907; Am. Jour. ofAnat., Vol. XI. 



