STEUCTURE AND DEVELOPMENTAL RATE 129 



Lot C5 at aboift 10°C. for four days, were possibly a little further 

 along then C4, though in general they showed a similar condition. 

 These were also returned to room temperature. 



Lot Di contained full-length embryos, some with the optic processes 

 already formed and others without. These specimens were about 

 one and a half days behind the control or about in the stage of the two 

 and a half day control. 



Lot D2, after four days at a temperature of 7°C., introduced after 27 

 hours of normal development, were still in about the same stage as 

 when placed in the refrigerator. The segmentation caps were flat with 

 early germ-rings forming and the embryonic shields just beginning. 

 The descent of the germ-ring has been considerably prevented. All 

 of the specimens were living and seemed well. They were now returned 

 to room temperature. 



Lot D3, all seemed in good condition with germ-rings from one- 

 quarter to one-half over the yolk-sphere and with well-formed embryonic 

 shields. Thus this slightly higher temperature of 8°C. had given the 

 D3 group a considerable advantage in progress over the D2 lot. These 

 were now also returned to room temperature. 



When six days old, the black and red chromatophores were fully 

 expanded on the yolk and embryonic bodies of the control specimens. 

 The embryos were now occasionally twitching and moving their 

 bodies. 



Lot Ci, after being out of the refrigerator for 3 days, had embryos 

 comparable to about a usual midsummer 70-hour stage, or about the 

 condition of the present control when 4 days old. The heart beat had 

 not begun. 



Lot C2, embryos were also in a stage just prior to the heart beat, 

 and the C3 group was about the same. 



Lot C4 were now out of the refrigerator for one day after having 

 been at a temperature of 9°C. for 4 days. The embryos were well 

 formed and the blastopore was about closing, so they had made a 

 considerable advance from the condition of the previous day when the 

 germ-rings were only one-half way over the yolk. The C5 group are 

 still further advanced with the optic outpushings prominently shown. 



Lot Di now showed chromatophores both on the yolks and on the 

 embryos' bodies, yet no heart beat could be detected in any of those 

 examined. 



Lot D2, when one day at room temperature after being at 7°C. for 

 four days, showed the germ-rings two-thirds over the yolk-sphere, 

 with the embryonic axis well formed in the shield. 



Lot D3 contained long embryos with the optic outpushings just 

 beginning, so these were still ahead of D2. 



At seven days the control embryos were actively moving and the 

 yolk vessels were now clearly mapped out by the pigmented arrange- 

 ment. 



Lot Ci, now out of the refrigerator for 4 days, showed many em- 

 bryos with good circulations and pigment migration, some had a 



