The Influence of External Factors on Development 183 



Solutions of KCl in distilled or sea-water caused the eggs to 

 develop at a slow rate, the yolks were shrunken and bubble-like 

 appearances were often seen below the embryonic shield. When 

 studied in section these eggs showed the following conditions: 

 The periblast beneath the embryonic shield had become vacuolated 

 with huge cavities in it as shown in Fig. 10. It thus bulged into 

 the yolk mass and the cavities produce the bubble-like appearance 



Fig. 10 A section of the embryonic shield from an egg thirty hours old in a | ni sea-water solution of 

 KCl, showing huge vacuoles v in the periblast beneath the shield. X 58^ diameters. 



Fig. 1 1 A section of the blastoderm of an egg thirty-one hours old that had spent the first twenty- 

 three hours after fertilization in a yV m MnCl^ solution. The central periblast, cph shows much 

 thickened, with many large nuclei accumulated in this region, c, Cavity in the blastoderm. X 58 j dia- 

 meters, 



seen in living eggs. The embryos are always much dwarfed and 

 pale. The heart never contracts although the embryo may 

 remain alive for as long a period as two weeks. The pericardium 

 is often puffed out and is unusually prominent, as also occurs in 

 some other solutions, as shown in Fig. 12, pc for an embryo from 

 a mixture of MgCl, and NaCl. 



