correspondence is to be interpreted as evidence of homology of the 

 structures in the two groups of animals. 



To show that my own independently reached results are in accord 

 with those ofDawydoff, Iquote from manuscript of my monograph on 

 the Enteropneusta of the Pacific Coast of North America, now ready 

 for the printer. The quotation has particular reference to a species of 

 Balanoglossus [B. occidentalis), and was written more than a year ago. 

 The accompanying figures are from transverse sections of the proboscis 

 of the same species. 



"It will be observed that in the section just referred to (Fig. 1) 

 the heart, h, appears as a wholly closed vesicle lying within the peri- 

 cardium, p c. 



Five sections faither back (Fig. 2) in the same series it is found 



Fig. 1. 



Fig. 2. 



that a narrow communication, c.?n., exists between the heart and the 

 great blood sinus of the glomerulus, gl. In other words the heart 

 is a nearly closed sac formed by the folding into its own cavity of the 

 ventral wall of the pericardium. The very thin wall of the heart, 

 h.ep.j is readily traceable around into direct continuity with the wall 

 of thè pericardium pc. ep. 



By following the series of sections still farther back, with the in- 

 crease in size of the notochord the usual enteropneustic relations of 

 heart, pericardium, and notochord, n. ch. come to view (Fig. 3). 



The heart, then, is here the ventral wall of the pericardium 

 pocketed into the pericardial cavity, the mouth of the 

 pocket remaining open backward and laterally, though 



