Hyatt,] 136 [March 15, 



He dealt with all tlie points treated of in Mr. DalFs communica- 

 tion, by reading, in both cases, Mr. Dall's first paper and his last 

 communication side by side, and submitting the facts to the Society 

 as to what Mr. Dall really said in his first paper, and the denials to 

 the same in this last communication. As to Mr. Dall's personal 

 opinions regarding improved homologies, and the doubts expressed 

 regarding certain well known structural features of the Brachiopods, 

 Mr. Morse would pass them over as the result of haste in discussing 

 the question. 



Prof. Hyatt said 



My objections to Mr. Morse's classification have heretofore rested 

 wholly upon the presumed affinities of the Polyzoa and Ascidia. I 

 have been led by the similarities of the adult animals of the two 

 groups, to partially follow Prof. Allman in his opinion, that these two 

 groups are closely related. In a paper on the fresh water Polyzoa 

 (Proceedings Essex Institute, Vol. iv.) I have compared them, but 

 at the same time shown that the differences are much greater be- 

 tween the Polyzoa and Ascidia than between the former and Brachi- 

 opods. Thus, there is no muscular system in the Ascidia which can 

 compare in any sense with that of the Polyzoa; and in transforming 

 the Polyzoa into an Ascidian, Prof. Allman is obliged to violate this 

 obvious difference, as well as to effect many changes which are not 

 consistent with their organization. The nearer affinity of the Poly- 

 zoa and Brachiopoda is hardly questionable, since the investigations 

 of Kovalewsky, who has shown us that the young Ascidians are ap- 

 parently more like young vertebrata than they are like the young of 

 the Polyzoa. The importance and value of the resemblances exist- 

 ing between the adult Polyzobn and the adult Ascidian, so far as they 

 may be supposed to indicate any close affinity or community of origin, 

 are thus doubly denied by the differences of form and structure, both 

 in the adults and in the larvae. 



The Ascidians are also likely to be removed by these new discov- 

 eries, not only entirely away from the Polyzoa, but to an equal or 

 greater distance from all the rest of the Mollusca; and even if we 

 could, in the face of embryology, still maintain our comparison be- 

 tween the two structures, we should be contrasting the Polyzoa, not 

 with a typical Mollusk, but with an animal whose own position is 

 very uncertain. I can think of no fundamental molluscan character- 

 istics, either in the Brachiopods or Polyzoa, which ally them with the 



