184 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



to know the species hj its botanical name. I leave its identification for 

 the cryptogamic botanists ; practically, a knowledge of its life-history 

 sufiices for our i^nri^oses. 



The following record of the most salient features of my observations, 

 made in association with Colonel McDonald, is on the whole not as en- 

 couraging as the experiment made at Havre de Grace, but it is of value 

 on account of the pathological changes or deformities which it was found 

 were induced in embryos when they were subjected to too low a temper- 

 ature. Only in the very late stages did they appear to be comparatively 

 free from this influence tending to the production of deformities. 



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

 mally develoi^ed were placed on trays in the refrigerator in the evening, 

 in an air temperature of 45° E. ; they were found in apparently normal 

 condition aft,er 24 hours had elapsed, but had made little or no progress 

 in development. After 24 hours more, or after exposure for 48 hours 

 to an air temperature of 45° F. on damp cloth trays, the germinal disk 

 was found to be deformed and dead, being helmet-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 enveloping them in a normal way. 

 Of the same lot, those which were taken out of the air temperature of 

 45° F. aud put into water at 74° F., hatched out normally in a good 

 jjercentage without deformities, showing that a suc^den transfer to water 

 at a much higher temperature was not attended with difficulties. The 

 I)rolonged stay of 48 hours of the same lot in the refrigerator at 45° F., 

 showed that complete arrest of development and death would super- 

 vene, and that a i^rofouud abnormal 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 rapidly. 



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. Tlie abnormal phenomena which 

 were noticed principally affected the notochord or embryooic axial car- 

 tilaginous rod, which had a tendency to become bent aud 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 micro-photograph of an embryo 

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

 ^0 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 



