The Influence of External Factors on Development 185 



hours. Eggs that were subjected to J m CaCla one hour after 

 fertihzation were almost all dead within four hours, the living ones 

 were abnormal, and all died after twenty-four hours. This result 

 further illustrates the readiness with which the egg membrane is 

 penetrated during the first few hours after fertilization. A mixture 

 of 60 cc. i m CaClz and 10 cc. i.o m NaCl proved equally as 

 fatal as the CaClj alone had done, neither of the cations seem to 

 exert an anti-toxic action toward the other. 



Solutions of NH4CI in distilled water of concentrations tV m, 

 T m, T m, i m, J m and ^ m were used; a molecular solution of 

 NH4CI is equivalent to about a 5.05 per cent solution. Sea-water 

 solutions of i m, ^ m and f m were also employed. These solu- 

 tions seemed to cause the yolk to shrink slightly, the blastoderm to 

 thicken so that on examining the living eggs one would think that 

 the segmentation cavity was abnormally large as it is in the lithium 

 embryos. On studying sections of these, it was found that the 

 cells are loosely connected, making the blastoderm unusually thick 

 so that it projects down into the yolk. The segmentation cavity 

 is, therefore, not abnormally large as in the lithium embryos. 

 Many of the eggs die at various stages. The rate of development 

 is retarded and the blastopore is slow to close. Many of the 

 embryos are short with their tail ending abruptly. In some 

 embryos the heart beats slowly and the circulation is sluggish; in 

 others there is no pulsation at all, and still others in the same 

 solution may show a very good circulation. Embryos lived as 

 long as eighteen days in such solutions but failed to hatch. 



Such short embryos as those above described seem to result 

 from any cause that retards development and prevents the nor- 

 mal down-growth of the germ-ring. When such embryos were 

 removed from | m NH4CI solutions when forty-three hours old 

 and placed in sea-water, they recovered in one day and hatched 

 when fourteen days old. The embryos in NH4CI are always 

 dwarfed, with poor circulation, lightly colored blood, and sparse 

 pigmentation, having a pale appearance. The sea-water solutions 

 of NH4CI were much less toxic than the distilled water ones. 



Mixtures of NH.Cl i m + MnCl^ 2V m, NH, CI i m + 

 • MnClj 2V m and NH.Cl i m + MnCl^ 2V m were tried. The 



