DEVELOPMENT OF FISH EMBRYOS 297 



a circulation of the blood in the vessels. In spite of this 

 fact, a complete circulatory system was developed which did 

 not differ markedly, in regard to the direction and the 

 branching of the vessels in the embryo and in the yolk-sac, 

 from that of a Fundulus embryo developed in normal sea- 

 water. Heaps of red-blood corpuscles -were found in the large 

 blood-vessels, such as the arteries of the yolk at the point 

 where they leave the embryo. 



The important result of these observations is therefore 

 the fact that a complete vascular system, which is probably 

 identical in its main distribution and in its two vascular 

 divisions with that found in the normal embryo, can be 

 formed without a circulation, and therefore without blood- 

 pressure. A difference between the two, which also deter- 

 mines the limit of the possible identity of the vascular sys- 

 tems in the normal and abnormal embryos, is found in this, 

 that the lumina of the vessels in the poisoned embryo are 

 exceedingly irregular. The lumen of a vessel is in extreme 

 cases rosary-like, narrow and wide spots alternating with 

 each other. This is due to the absence of a sufficient intra- 

 vascular pressure. 



3. It might have been possible that a circulation lasting 

 only a short time had been present which I did not dis- 

 cover. I therefore made experiments with much stronger 

 KC1 solutions such in which not even a trace of cardiac 

 activity ever appeared. In extreme cases I addded 5 g. of 

 KC1 to 100 c.c. of sea-water. I had previously ascertained 

 that a four-day-old embryo which had developed in normal 

 sea-water dies in two minutes in a 3 per cent. KC1 solution. 

 Nevertheless, the fertilized eggs developed normally in a 5 

 per cent. KCl solution. They developed for three to six 

 days, and formed what is of interest to us here a heart 

 and a typical vascular system in the embryo and yolk-sac. 

 On the other hand, the development of the embryo as a 



