Gr. Y. and A. F. Dixon — On Bunodes thallia, etc. 319 



mesenteries of the directive pairs corresponding to these two 

 grooves gradually diminished in size, and, eventually, failing to 

 reach the oesophagus, became irregularly united by their free 

 margins with each other, and with the three enclosed pairs of 

 mesenteries. Thus we found, corresponding to what was here a 

 single groove, a pair of directive mesenteries, with a series of 

 smaller mesenteries interposed between them (PL iv. fig. 8). 



Of the pair of directive mesenteries in the remaining specimen, 

 one mesentery was rudimentary, and never reached as far as the 

 oesophagus, while the other was fully developed. 



Circular Muscle. — There is a strongly- developed endodermal 

 circular muscle lying in the corner formed by the oval disk and 

 the body wall. In logitudinal sections of the animal it bears a 

 general resemblance to that figured by Professor Hertwig in 

 Tealia ftunodiformis, but we have been unable to discover any 

 anastomosis of the pleatings of the mesogloea. 



The result of the foregoing observations is to establish a close 

 relation between Bunodes thallia and Tealia bunodiformis. In one 

 point only is there considerable divergence between Professor 

 Hertwig's description of the " Challenger " form and the account we 

 have given above. Professor Hertwig says the warts in Tealia 

 bunodiformis are irregularly scattered with a tendency to arrange- 

 ment in longitudinal rows, while in Bunodes thallia we have found 

 that the warts are arranged in regular vertical series. It was long 

 believed that in Tealia crassicornis the warts were irregularly 

 scattered, but we believe that even, in that species too they are 

 vertically arranged in the endocoeles, and that the apparent 

 irregularity in arrangement is due to the unequal expansion 

 of the animal. We have been led to this conclusion from a 

 careful examination of some young specimens of this well-known 

 species which we shall presently describe. 



With all respect to such an experienced observer as Professor 

 Hertwig, we would venture to suggest that the three specimens of 

 Tealia bunodiformis which came into his hands were unequally 

 contracted, and that hence the warts, though vertically arranged 

 in the endocoeles, were apparently irregularly scattered. Of 

 course if we are right in identifying the warts with the " endo- 

 dermal saccules/' it is plain that they are regularly arranged, for 



