OF ARTS AND SCIENCES. 65 



the kidney. This arborescent character of organic development, 

 homologous perhaps with the branching of polyps, reduces 

 the process of development to an extremely simple formula. 



Professor Agassiz observed that the heart, which he had 

 studied especially in fishes, makes its first appearance as a 

 mass of apparently homogeneous cells ; the interior cells grad- 

 ually soften, forming a cavity, the walls being at the same 

 time proportionally solidified. He did not perceive the ho- 

 mology of the ramification described by Dr. Burnett to the 

 branching of polyps ; the buds of a polyp are not hernial sacs 

 communicating primarily with the parent stem, but solid tu- 

 bercles formed on the outside, gradually becoming hollow and 

 communicating only secondarily with the main trunk. 



Professor J. Wyman asked if, in the development of the liver, 

 the cells were first formed, and the tubes extended from the 

 intestine to meet them, as BischofF maintains. Dr. Burnett 

 had made no observations on this point in the vertebrated 

 animals. 



Professor Agassiz made a communication on a new living 

 species of Cestracion from China, and on some fossil teeth of 

 sharks of this family which he had received from the carbonif- 

 erous formation of Indiana. From the examination of these 

 specimens he thinks that all the genera but one — which he 

 made long ago from the scanty materials in Europe (only a 

 single jaw and some dried skins) — will stand ; of the species 

 he is not so confident. 



The new species, from its distinct bands, he would call Ces- 

 tracion zebra. It is thus characterized : a square-shaped head 

 resembling that of Ostracion; the nostrils open into the mouth 

 by a strong fissure ; the mouth is small, more anterior than 

 usual ; there are singular cheek-like projections on the sides 

 of the head ; the body is massive, and much elevated on the 

 back ; the dorsal fins much falcated, especially the second ; 

 the gill fissures are usually in advance of the pectorals, but in 

 this species the pectorals begin anteriorly under the third 

 gill-fissure ; the spiracles open below the eyes ; the caudal fin 



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