STRUCTURE AND DEVELOPMENTAL RATE 151 



yolk, and 13 had died or failed to resume development. Therefore, in 

 this lot 66 per cent were able to resume development, which is a some- 

 what better record than the B series. This difference may easily be 

 due to individual variations between the two lots of eggs from the two 

 different pairs of fish, yet both lots of eggs were unusually fine, as was 

 shown by the perfection of the B control as well as the C. 



When 10 days old the controls were going perfectly and seemed 

 about at the point of hatching, having grown long with the tails curved 

 around to cover the side of the heads, j^et the yolk-spheres were still 

 rather large. 



In lot Bi 7 of the 9 living eggs showed embryos almost normal in 

 appearance with good circulations, one was badly deformed and had a 

 pulsating heart, but no circulation, while the one yolk-sac without an 

 embryo had not progressed in development. 



Lot B2 showed 36 strong embryos with good circulation, though one 

 of these was slow, with eyes abnormally close together. Four speci- 

 mens Avere badly deformed, one with a circulation of the blood and 

 three without. There were two yolk-sacs with blood and pigment 

 cells present and two others did not develop. Thus 42 eggs were still 

 alive, of which 7, or 16| per cent, were grossly deformed. 



All eggs in lot B3 seemed normal and well, although far behind the 

 control. 



In lot Ci 15 specimens seemed normal in structure, though two of 

 these were slower than others in development. Ten specimens, or 40 

 per cent of the total, were deformed, 8 showed grossly malformed heads 

 and bodies, one embryo being represented by an amorphous mound of 

 tissue on the yolk-sac, and two other specimens had only deformed heads 

 with a fair circulation of the blood. Thus in this lot where the mor- 

 tality following removal from the cold was low, the percentage of de- 

 formed specimens is two and one-half times greater than from the B2 

 lot that had suffered a high initial mortality. 



When 16 days old, the majority of both control lots had hatched, 

 though none of the inhibited ones had. When 17 days old, one in lot 

 Bo and 3 in lot B2 had hatched, though none in Bi and Ci. 



At 18 days old, the controls still had a few unhatched. 



In lots Bi 6 were hatched and 2 were not; in Bo 21 were hatched and 

 20 were unhatched; in B3 33 were hatched and 27 were not; in Ci 13 

 were and 12 were not hatched. 



When 24 days old, lot Bi contained one badly abnormal specimen 

 still unhatched. In lot B2 17 were still unhatched, 5 of these were 

 grossly deformed. In lot B3 12 were unhatched, though seemingly 

 normal in structure. These were all far behind the control in time and 

 manner of hatching. In lot Ci 8 were deformed and unhatched, and 

 one, slightly abnormal in gross appearance, partially succeeded in 

 freeing itself from the egg membrane. Thus really 9 of these were 

 deformed and unhatched. 



When 29 days old, one individual in the B control had not hatched 

 though the others had been free swimming for 10 days. This was the 



