1 86 Charles R. Stockard 



eggs lived better in these solutions than in either the NH^Cl 

 or the MnCU. The first twenty- four hours of development is 

 almost normal though some eggs die, the rate of development after 

 this period becomes retarded, the embryos have swollen pericardia 

 in some cases, and are pale and small. Some of them continued 

 to live in these solutions for fifteen days but were far from the 

 hatching stage at this time. The weaker toxicity of these mixtures 

 when compared with the action of the salts used singly may be due 

 as Loeb ('02) has claimed, to an anti-toxic effect of one ion on the 

 other. The mixtures with less NH^Cl were always less active, 

 Loeb found the bivalent cations to show an anti-toxic action 

 toward the monovalent ones. 



MnCl, solutions were used of the strengths 2V m, yV m, and yVm 

 in distilled water; and J^ m, yV m, and I m in sea-water. Eggs 

 that were subjected to the action of such solutions responded in the 

 following way: Those in the distilled water solutions go normally 

 for several hours, then w^hen about eighteen or twenty hours old 

 the blastoderm shows a dark central portion when viewed from 

 above, while in side view it shows that the dark area protrudes 

 downward into the yolk. A section of such a blastoderm is seen 

 in Fig. II. The dark area is shown to result from an unusual 

 thickening in the center of the central periblast, cpb, and the 

 accumulation at this point of a number of the large periblast nuclei. 

 A slight cavity, <:, is not uncommon near the surface of the blasto- 

 derm. This unusual thickening of the periblast seems to render 

 difficult the subsequent descent of the germ-ring, and development 

 is thus slightly retarded. When about forty hours old many 

 embryos have their germ-rings only one-half over the yolks, and a 

 short embryo is outlined on the embryonic shield. Many of the 

 eggs died in these solutions. The embryos have a feeble pulse and 

 the blood is often clotted in some of the larger vessels. When 

 fifteen days old embryos hatched in the 75 m solutions but swam 

 abnormally; one embryo w^as seen to hatch in a yV m MnCl 2 solu- 

 tion but it was entirely unable to swim. 



The solutions of MnCK in sea-water formed slight precipitates 

 and the results are thus no doubt vitiated to some extent, neverthe- 

 less the dark central portion of the blastoderm always showed. 



