IX 
ON THE DEVELOPMENT OF FISH EMBRYOS WITH 
SUPPRESSED CIRCULATION! 
1. One of the methods which may lead us deeper into the 
physiology of development consists in removing one link in 
the chain of such processes in order to see how the further 
development is influenced by such a step. I recently came 
upon such an experiment, which I wish to detail in the fol- 
lowing pages. The experiment consisted in preventing, by 
a specific cardiac poison, the beat of the heart and the circu- 
lation of the blood in an embryo. I had, indeed, expected 
that under such circumstances the embryo would not die 
immediately, but I did expect that its further development 
would certainly be impossible. In this, however, I was mis- 
taken. Development went on in spite of the elimination of 
the activity of the heart; in some cases as long as four days 
—which was nearly half, or one-third, of the duration of the 
embryonic stage. The consequences of the elimination of 
the activity of the heart are also in some ways different from 
what one might expect. The observations have not been 
completed on all points because of the lateness of the season 
and lack of material, but I intend to fill in these gaps next 
season. 
The experiments were made upon a marine fish, Fundu- 
lus, which is very common at Woods Hole. The eggs were 
fertilized artificially in normal sea-water. Jn order to 
prevent the action of the heart and the circulation in the 
developing embryo, the eggs were put, half an hour after 
fertilization, into sea-water to which a sufficient amount of 
potassium chloride had been added. Potassium chloride can 
1 Pfitigers Archiv, Vol. LIV (1893), p. 525. 
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