450 WM. E. KELLICOTT 



In a word the method consists simply in subjecting the fer- 

 tiUzed ova or young embryos to the temperatures of the ordinary 

 household refrigerator, namely, 8-1 3°C. for a few hours or days. 



In connection with the work on Teleosts in the Embryology 

 Course at The Marine Biological Laboratory, we have for several 

 seasons made a practice of placing the eggs, at various stages of 

 development, in the refrigerator in order to slow their develop- 

 ment and thus secure certain stages at hours convenient for 

 study. It was noticed that a sUght reduction in temperature 

 merely slowed development without leading to any serious dis- 

 turbance in morphogenesis, while a few hours at a temperature 

 below 12-14°C. were followed, upon returning the eggs to the 

 laboratory, by a considerable mortahty and by very frequent 

 abnormality (the eggs of Tautogolabrus (syn. Ctenolabrus) , not 

 Fundulus, were then used). In fact abnormalities in nuclear 

 and cytoplasmic arrangements were to be noted while the eggs 

 were still at the lower temperature. It was not until last sum- 

 mer, however, that the more precise examination of the results 

 of this treatment was undertaken. While these experiments 

 were in progress Loeb ('15) reported certain observations on the 

 effects of much lower temperatures upon the development of 

 Fundulus. His results will be discussed and compared with my 

 own later in this paper. My apparent neglect to test certain 

 points of disagreement is due merely to the fact that his paper 

 did not come to my attention until some time after the spawn- 

 ing season of Fundulus was entirely past, which made such an 

 attempt impossible. 



The eggs were inseminated in the usual manner, i.e., diy, 

 with the addition of testis teased in only a few drops of sea- 

 water. They w^ere placed in finger bowls with a half-inch or so 

 of water; the bowls were covered to prevent evaporation, and 

 placed on the shelves of the refrigerator. The range of tem- 

 peratures used was secured merely by using higher or lower 

 shelves, in compartments alongside or below the ice compart- 

 ment. The water was renewed daily, or in some instances 

 every other day, the fresh water being at the refrigerator tem- 

 perature. That covering the bowls with glass plates did not 



