DEVELOPMENT OF VESSELS WITHOUT HEART 



181 



Fig. V Camera lucida drawing of an injected, normal chick of 35 hours incu- 

 bation, 16 somites, cleared in oil of wintergreen, viewed from above. The left 

 half of the area is shown. Enl. 12't X. 



1 The chick shown in figure 1 was incubated 3.5 houi's, but in development has 

 reached the stage usually seen in chicks of about 38 hours incubation. It is, 

 therefore, slightly older than most of the chicks at the time of operation. The ink 

 was injected into the sinus terminalis and forced through the capillary net, or, 

 as I have termed it in the text, the venous plexus of capillaries anterior to the 

 embryo, to the rudimentary vitelline veins. Ink was also introduced into the 

 heart. The heart pumped the ink back and forth into the sinus and vitelline 

 veins for several minutes, but soon particles of the ink began to shoot through the 

 arches into the right dorsal aorta. This was followed quickly by a rapidly grow- 

 ing stream of ink which moved forward as propelled* by the pulsating heart and 

 spread out into the capillary net at the termination of the dorsal aorta several 



AMERICAN- JOUKNAL OF AXATOMY, VOL. 23, NO. 1 



