ORIGIN OF VASCULAR TISSUES 109 



treatment which will prevent circulation. If differentiation can 

 proceed further in cardiectomized embryos, it is not unreasonable 

 to believe that the process there is more nearly normal. It is 

 practically certain that the normal process of hematopoesis is 

 not duplicated in either case of abnormal treatment. So far, 

 the most anterior erythrocytes obtained in cardiectomized em- 

 bryos are located ventro-mesial to the anterior portions of the 

 otocysts. None has yet been found in the ophthalmic region and 

 in the snout. These experiments were not begun, however, until 

 late in the spawning season of Fundulus. Fifteen hundred car- 

 diectomies were performed with only partial success, so that it 

 is impossible to predict at present the possibilities of this method 

 of experiment. A very few embryos survived the operations. 

 Those embryos which fail to withstand such treatment generally 

 die soon after the operation. In most of the survivors, erythro- 

 cytes could be seen in the living condition much anterior to the 

 pectoral fins. Most of the present descriptions are based on the 

 living conditions. So far, very few of such embryos have been 

 sectioned. Thus it is conceivable that some of the embryos now 

 preserved may exhibit erythrocytes farther anteriorly than have 

 yet been figured in case of cardiectomy. Only three of the em- 

 bryos will be described at present. 



Figure 82 shows the living condition of a nine-day embryo, the 

 heart of which was removed when the embryo was sixty hours 

 old. The heart had not yet pulsated. Following the operation 

 the embryo was kept in a moist-chamber in a cool place. The 

 tail of the embryo became rather long and curved over the dor- 

 sal body-surface. The embryo could not be provoked to reflex- 

 responses, and never exhibited any movement. The pectoral 

 fins were relatively huge, working in unison with a quivering 

 fan-like movement. Very well differentiated striated muscle de- 

 veloped at their bases. It will be noted that the head is rela- 

 tively small ; at the anterior limits of the otocysts it narrows down 

 so that its diameter in the region of the eyes, as seen from the 

 dorsal side, is less than half that of the region of the otocysts. 

 The eyes are merely rudimentary optic stalks. There are neither 

 optic cups nor lenses. The pericardium is oedematous. It con- 



