360 



(2) Firstly, I have been led to agree with the second of Dr. H ar- 

 mor's formulae, for the simple reason that I have been enabled to 

 distinguish the true pericardium (Herzblase) occupying a considerable 

 portion of the subneural sinus. Its relationships appear to be almost 

 those suggested by Dr. H armer, so far as one can judge. He re- 

 marked »I can quite confirm the accuracy of Mr. Masterman's 

 description in most of these points, but I believe that his subneural 

 sinus is the heart-vesicle, and therefore not a part of the vascular 

 system; and that the structure which projects into it is the central 

 blood-space ofSpengel, which in Balanoglossus communicates with 



the dorsal blood-vessel I must however admit that I have not 



been able to convince myself with certainty that the central blood- 

 space opens into any other vessels, though I have some slight evidence 

 pointing in that direction.« (p. 345.) 



I hope to be able to demonstrate the communications of this 

 "heart" with the rest of the vascular system, which seem to be effected 

 in a somewhat peculiar manner. In answering Dr. Harm er I remar- 

 ked "immediately after the first examination of my sections of Cephalo- 

 discus I supposed that the organs brought to view had exactly the 

 structures and homologies since suggested by Mr. Harmer, but a 

 closer inspection proved them to be untenable. " (p. 444.) So far was 

 this the case that in my first series of drawings the "heart" is coloured 

 red and labelled as such. How is it possible then that I could find 

 sufficiently strong evidence firstly to deny Dr. Harm er 's statements 

 and now in the main points to corroborate them ? The evidence, for 

 or against, depends upon the presence or absence of communications 

 of one part with another and, as Dr. Harmer remarks, "the small 

 size of the parts in question make it very easy, to be misled in regard 

 to the way in which one space communicates with another;" but this 

 is not all, for re-inspection of my former sections of the first 5 or 6 

 specimens I had available shows quite clearly the communications re- 

 ferred to. In fact, in both the longitudinal and transverse sections 

 the lumen of the pericardium "is perfectly continuous with the dorsal 

 blood vessel". Sections of some fresh material, however, in at least 

 one clear case, show an extremely delicate but intact posterior wall to 

 the pericardium, separating it from the dorsal blood vessel. This 

 posterior wall is thinner than the mesenchymatous strands crossing 

 the lumen. Under such circumstances one must assume that its ab- 

 sence in the others is due to extensive rupture leaving little or no 

 trace of the dividing wall. 



(Schluß folgt.) 



Druck von Breitkopf & Härtel in Leipzig. 



