The Influence of External Factors on Development l8l 



ing short embryos. In Li2S04 xV rn some are dead, others have a 

 polar cap with an embryo forming in it. Of those in LizSO^ ttV m 

 some are dead, others are with the blastopore almost closed, but 

 the embryos show no optic vesicles as yet, a few have polar caps 

 with embryonic thickenings in them. 



When seventy-two hours old, the eggs in LiNOg i m have some 

 embryos almost as long as those of the control but with no circula- 



Fig. 5 An egg from aim LiNOa solution twentj'-three hours after fertilization. sc, segmentation 

 cavit}'; od, oil drops. 



Fig. 6 From a jV ni LiNOs solution when twenty-three and one-half hours old. 



Fig. 7 From a -,'q ni Li2S04 solution at twenty-three hours old sc, segmentation cavity. 



Fig. 8 From a -^^ m Li2S04 solution at twenty-three and one-half hours old. 



Fig. 9 A control egg of twenty-three hours. All magnified 17^ dia. 



tion apparent; the heads are poorly formed and show no optic 

 vesicles in surface view. In the LiNOj 2^8 m solutions all of the 

 eggs are dead. In Li2S04 tV m some have the germ-rings only 

 one-halfway over the yolk, with short embryos formed; in others 

 development has stopped. In the Li2S04 to m solution most of 

 the eggs are dead though a few have badly twisted embryos with 

 poorly formed heads and no optic vesicles. 



