237 



surface is in and around the Gulf of Mexico ; that exposed 

 to the most violent and repeated shocks, the Javanese Archi- 

 pelago, of which the island of Sumbava forms nearly the cen- 

 tre; while, probably, the most interesting earthquake tract 

 now known is the great submarine one in the Atlantic Ocean, 

 in latitude 0° to 1 1° south, and west longitude, from 20° to 23° 

 or 24°. 



The places on the earth's surface as to which earthquake 

 information is most wanted, and to be commended to the atten- 

 tion of travellers are, the great Ethiopian chain of mountains, 

 and interior of Africa generally, Madagascar, Central and 

 Northern Asia, where the earthquake regions seem to follow 

 the courses of the great northern rivers, north of Lake Baikal, 

 the north-west of North America, the Gallipagos Islands, and 

 in Europe, Spain. 



The President made some remarks upon Mr. Mallet's 

 Paper. 



Dr. Alhnan read a paper on the Homology of Organs and 

 the Affinities of the Polyzoa and Tunicata. 



In this communication it was the author's object to demon- 

 strate that the affinities between the Tunicata and Polyzoa 

 were even closer than what was generally imagined, and that 

 almost every portion of the organization of the one had its cor- 

 responding homologue in the other. The hippocrepean Poly- 

 zoa are those which indicate most clearly the unity of type on 

 which the two groups are constructed, and a comparison was 

 therefore instituted between a Clavelina and a Plumatella. It 

 was shown : — 



1 . That the respiratory sac of the one was in every parti- 

 cular homologous with the tentacular crown of the other; that 

 the arms of the lophophore in Plumatella were represented by 

 the "branchial sinus" in Clavelina, the tentacula in Plumatella 

 by the transverse bars or vessels which spring off from each 



