298 STUDIES IN GENERAL PHYSIOLOGY 



whole was markedly retarded in this concentrated salt solu- 

 tion, so that a definite judgment of the vascular system could 

 be made only so far as the main stems and their branches 

 were concerned. These main stems corresponded with the 

 main stems of the normal embryo. Yet I was never able to 

 discover even the slightest evidence of a heart-beat, much 

 less a circulation. The lack of hydrostatic pressure within 

 the vessels was particularly evident here from the irregularity 

 in the diameter of the blood-vessels; nevertheless, a large 

 number of branches, which gradually decreased in caliber, 

 sprang from the main vessels. In this case, therefore, it is 

 unquestionably true that the process of branching and the 

 growth of the blood-vessels are independent of blood-pres- 

 sure. 



4. The experiments with weak KC1 solutions also deserve 

 mention. In a series of experiments I added 0.25 to 0.5 g. 

 to 100 c.c. of sea-water; normal development occurred in 

 these solutions. The heart-beat and the circulation 

 developed apparently normally. The control eggs, which 

 had been taken from the same culture, but raised in normal 

 sea- water, completed their development in twelve to sixteen 

 days, when the embryos hatched. They lived some four to 

 six weeks after escaping from the egg. In the two KC1 

 solutions, however, but one embryo, which lived for a day, 

 hatched on the twelfth day in the 0.5 per cent. KC1 solution. 

 All the remaining embryos died between the twelfth and 

 sixteenth day. Death unquestionably resulted from a 

 poisoning of the heart, and not from a general intoxication. 



5. The experiments cited above show thai a KC1 solution 

 of a definite constitution is the more poisonous the older the 

 embryo. . One might think that the chemical constitution of 

 the individual elements of the heart changes with develop- 

 ment ; but how can we harmonize with this the fact, which 

 has been mentioned above, that the heart of a four-to-five- 



