ORIGIN OF BLOOD AND EXDOTHELIUM 



19 



ht 



Fig. 1 The head end of a normal Fundulus heteroclitus embryo from life, 

 five days old; ht, the heart, showing its S-shape; e, eye; o, ear. 



Fig. 2 From a living embryo of the same age, developed in a weak solution 

 of alcohol; the blood does not circulate and the body is small; ht, the heart 

 stretched into a straight tube surrounded by a much dilated pericardium; ch, 

 small and unexpanded chromatophores. 



Fig. 3 The head end of a five-day embryo without a circulation, from a weak 

 alcohol solution; ht, the heart slightly projecting from beneath the head. 



Fig. 4 A five-day embryo from a stronger alcohol solution; the eye is cyclo- 

 pean, the posterior end of the body split, cauda-bifida, and no blood circula- 

 tion. Pigment cells are collecting about the sinuses; PC, distended pericardium; 

 Kv, Kupffer's vesicle, also hugely distended. 



