LOW TEMPERATURE — DEVELOPMENT OF FUNDULUS 455 



I am entirely at a loss to interpret the difference between 

 Loeb's observations and my own on this point. It is just pos- 

 sible, referring to the latter instances mentioned above, that at 

 a temperature of only 0-2°C. the living processes of the embryo 

 are so completely stopped that when development is resumed at 

 a higher temperature no disturbing effects are to be seen; in 

 other words not even abnormal development may proceed at so 

 low a temperature. But this possibility seems largely negatived 

 by the observation that extremely harmful- results follow simi- 

 lar treatment of uncleaved or four cell stages. And no such 

 interpretation seems possible for his results at 7°C., which should 

 be more nearly comparable with my own at 8-10°C. I ob- 

 served no instance of normal development occurring after eggs 

 had been three weeks at 8-10°C., although several lots of eggs 

 were tested and among the same lots normal development some- 

 times followed briefer treatment; and abnormalities were very 

 common after treatment for only twenty-four hours, in some lots 

 even for only five and one-half hours. Two lots of eggs, treated 

 in just the same manner as the others, showed no abnormalities 

 upon development after twelve hours at 8-10°C. It seems quite 

 unlikely, however, that all of Loeb's material could have been 

 so unusually resistant, in view of the rarity with which such lots 

 came under my observation. I may add in passing that Wer- 

 ber ('15, b) notes that he too was able to secure abnormal em- 

 bryos by treatment with temperatures much higher than those 

 used by Loeb, but he gives no details either of his experiments 

 or results. 



It would not be profitable to attempt to describe in detail the 

 abnormalities observed, nor even to enumerate all of them. In 

 general it may be said that the embryos resulting from this 

 treatment showed every degree of abnormality, from irregular 

 masses of protoplasm, alive though exhibiting few of the char- 

 acteristics of organisms, up to completely normal hatched 

 larvae. Among several hundred embryos examined there was 

 fomid almost every conceivable kind of disturbance. Every 

 characteristic that could be observed externally with the lower 

 powers of the microscope showed some degree of abnormality in 



