1854.] Linnean Society. 301 



in some parts of its structure it approximates to certain of the Anne- 

 lides. A very beautiful and interesting fact was also observed by 

 this author in his examination of the development of Aplysia. This 

 is, the existence of a nautiliform shell, with an operculum perfectly 

 closing the mouth of the shell, and adherent to a part which 

 becomes the foot of the animal, — a very interesting proof that the 

 real affinities of Mollusca must be studied in their embryogeny. 

 But the discoveries by which he is perhaps best known and most 

 distinguished, are those on the impregnation and development of 

 diflferent forms of Polypes. In these researches many important 

 points in the physiology of these animals are established, and there 

 is a great degree of originality and ingenuity displayed in the 

 manner in which they were conducted and the results deduced. The 

 bisexual character of Alcyonella, the occurrence of distinct male and 

 female organisms on the same polypary, — the nature of the former 

 proved by its containing true zoosperms, — the existence of a circula- 

 tion and of a distinct nervous system in the same polype, its in- 

 dependent, and isolated, and free condition in the early stage of its 

 life, are all facts of great interest in the history of this tribe of 

 animals. I need only further refer to his researches on Campanu- 

 laria, which give the clearest exposition of a distinct metamorphosis 

 in the transition from the form, organization, aspect and habits of 

 the Medusae to the subsequent condition of the Polype. I need not 

 allude to the important bearing of these facts upon the question of 

 embryonic transformation, so remarkably illustrated in other forms 

 by the researches of Sars, of Loven, of Dalyell, of Steenstrup, of 

 Huxley, and many others. I must just glance at one more of this 

 excellent observer's demonstrations. In a paper on certain cestoid 

 worms, he shows that this form is nothing more than an early, but 

 not the earliest, condition of the Trematoda ; that, in fact, the Te- 

 trarhyncM are Scolex on their first evolution, Tetrarhynchi in their 

 second stage, Bothriocephali in the third, and finally Trematoda ; 

 and in the same group he has shown, by his observations on the de- 

 velopment of Linguatula {Pentastoma, Rudolphi), that by its embrvo- 

 logy it is nearly related to the Lernceadce, and thus removed from 

 the Helminthoid group, with which it had been pre\'iously asso- 

 ciated. 



In recommending to the Society the American traveller and na- 

 turalist James Dana, the Council were determined by numerous and 

 valuable works which have evinced a very extensive acquaintance 

 with systematic zoology, as well as with physical geography in its 

 relations to animal life. On the temperature limiting the distribu- 



No. LVII. — Proceedings of the Linnean Society. 



