G. NATURAL HISTORY AND ZOOLOGY. 315 



of the American Conchological Journal. The principal law 

 deducible from the- facts observed by him tends to show that 

 species, sub-species, and varieties, living in cool, damp situa- 

 tions, become more highly developed (but not always larger) 

 than others, the shell assuming a more compact (imperforate) 

 form, and losing those indications of immaturity referred to, 

 viz., sharp, delicate sculpture, bristles, and angular periphery. 

 These characteristics, however, remain more or less perma- 

 nently for indefinite periods, and give that fixedness to the 

 various forms, even when living under the same conditions, 

 which enables us to retain them as sub-species, differing from 

 varieties in permanency, and from races in not inhabiting dis- 

 tinct regions. Arionta arrosa and Lysines dupetithouarsi are 

 thus the most highly developed group in California. Proc, 

 Gal. Acad. Sci., V., 1 25. 



THE FOOD OF THE OYSTER, AND A NEW PARASITE. 



In a paper read before the Boston Society of Natural His- 

 tory, Professor John M'Crady treated of the food and repro- 

 ductive organs of the oyster, with an account of a new para- 

 site, as observed in oysters taken in Charlestown Harbor. 

 The oyster lives in the mud bottom, imbedded in a thick 

 layer of low organic forms, which covers the whole surface 

 of the mud as a yellowish organic film. The upper portion 

 of this growth is tenanted by diatoms, sporules of algre, and 

 by rhizopods, of which the former two, at least, seem to form 

 the principal food of the oyster. 



In the reproductive organ of these oysters a peculiar ento- 

 zoon was found, which, in its most advanced stage, is branch- 

 ed, with two long tentacle-like organs at one extremity. This 

 parasite appears for a time completely to destroy the fertili- 

 ty of the oyster; and to its abundance may perhaps be due 

 the seasons of short spawn often noticed by those engaged in 

 the oyster culture. This parasite has been named Bucepha- 

 lus cuculus. 



VOMITING A LIVER-WORM. 



At a late meeting of the Academy of Natural Sciences of 

 Philadelphia, Professor Leidy made a communication in refer- 

 ence to a worm vomited by a Chinese boy in Canton, and 

 which was transmitted to him for examination. He reports 



