802 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



value ou account of the pathological changes or deformities which it 

 was found were induced in embryos when they were subjected to too low 

 a temperature. Only in the very late stages did they appear to be com- 

 paratively free from this influence tending to the production of de- 

 formities. 



A lot of eggs which had the germinal disk biscuit-shaped and nor- 

 mally developed were placed on trays in the refrigerator in the evening, 

 in an air temperature of 45"^ F. They were found in apparently normal 

 condition after twenty-four hours had elapsed, but had made little or no 

 progress in development. After twenty-four hours more, or after expo- 

 sure for forty-eight hours to an air temperature of 45° F. on damp cloth 

 trays, the germinal disk was found to be deformed and dead, being hel- 

 met-shaped, with one or two constrictions or furrows running round it. 

 The vitellus or yelk still retained its normal appearance, however, the 

 vitelline spheres being clear, with the protoplasmic mesh-work envelop- 

 ing them in a normal way. Of the same lot, those which were taken out 

 of the air temperature of 45° F. and put into water at 74° F. hatched 

 out normally in a good percentage, without deformities, showing that 

 a sudden transfer to water at a much higher temperature was not at- 

 tended with difficulties. The prolonged stay of forty-eight hours of the 

 the same lot in the refrigerator at 45° F. showed that complete arrest 

 of development and death would supervene, and that a profound abnor- 

 normal change in the form of the germinal disk would result. 



Another series of experiments with eggs kept in a temperature of 

 64° F. showed the same tendency to retard development as was shown 

 by the Havre de Grace experiments. Embryos of the same age in water 

 at 74° F. developed nearly twice as rai)idly. 



Other experiments showed that eggs which had been retarded in de- 

 velopment at a temperature a little below 52° F. for two days exhibited 

 a tendency to develop abnormally. The abnormal phenomena which 

 were noticed principally aliected the notochord or embryonic axial car- 

 tilaginous rod, which had a tendency to become bent and twisted, while 

 constrictions were also apt to appear, giving it an irregular, beaded, and 

 generally misshapen appearance. Such deformities seemed to affect 

 only the caudal portion of the notochord, the portion toward the head 

 end of the embryo being normal in its appearance. In this way great 

 deformities of the tail arose, so that in a microphotograph of an embryo 

 two-thirds developed the tail, instead of being gracefully bent flatwise 

 to one side, is abruptly bent downwards and then upwards, so as to be 

 approximately V-shaped as seen from the side. 



Sometimes the deformation of the tail would only be noticeable at its 

 extremity ; at others the deformed portion of the notochord would ex- 

 tend some way forward over the yelk beyond the point where the tail 

 originated, as it budded out from above the point where the blastoderm 

 closed. In no instance was it observed that any deformity or disturb- 



