60 EECORD OF CUURENT RESEARCHES RELATING TO 



2. Segmentation takes place very rapidly, and follows substantially 

 the course described for other Lamellibranchs by Loven and Flemming. 



3. Segmentation is completed in about two hours, and gives rise 

 to a gastrula, with ectoderm, endoderm, digestive cavity and blasto- 

 pore, and a circlet of cilia or velum. At this stage of development 

 the embryos crowd to the surface of the water, and form a dense 

 layer, a little less than a quarter of an inch thick. 



4. The blastopore closes up ; the endoderm separates entirely 

 from the ectoderm, and the two valves of the shell are formed separate 

 from each other at the edges of the furrow formed by the closure of 

 the blastopore. 



5. The digestive cavity enlarges and becomes ciliated, and the 

 mouth pushes in as an invagination of the ectoderm at a point directly 

 opposite that which the blastopore had occupied. The anus makes 

 its appearance close to the mouth. 



6. The embryos scatter to various depths, and swim by the action 

 of the cilia of the velum. The shells grow down over the digestive 

 tract and velum, and the embryo assumes a form so similar to many 

 marine Lamellibranch embryos which are captured by the dip-net at 

 the surface of the ocean, that it is not possible to identify them as 

 oysters without tracing them from the egg. The oldest ones raised 

 in aquaria were almost exactly like the embryos of Cardium figured 

 by Loven. 



7. The ovaries of oysters less than 11- inch in length, and pro- 

 bably not more than one year old, were fertilized with semen from 

 males of the same sizes, and developed normally. 



A detailed account of these observations is to be published in the 

 Eeport of the Maryland Fish Commission for 1879. 



Molluscoida. 



N"ew Species of Polyzoa.* — Mr, C. M. Maplestone describes a now 

 species of Cheilostomatous Polyzoa, which presents peculiar features. 



Bicellaria annulata.— Cells elongated, contracted in front below, 

 aperture oval ; four to five marginal incurved spines on outside 

 edge ; one spine on summit of aperture extending behind superior 

 cell ; one spine on lower portion of aperture extending inward under- 

 neath marginal spines ; back of cell with a bifurcate elevation ; cells 

 growing on a corneous, tubular, spindle-shaped growth, with annu- 

 lated branches bearing cells. 



The peculiarity of the species is the structure upon which the cells 

 grow ; and from the ringed appearance of the individual spindles and 

 the more strongly annulated branches the specific designation is 

 derived. In fact the author almost thinks that a new genus is requisite 

 for its reception. 



Mr, J. E, Y, Goldstein also describes f a new species belonging 

 to the Gymnolasmata of Allman (suborder Ctenostomata, family 

 Serialaridce). 



Serialaria Woodsii. — Polypidom of a brown colour, light to dark; 

 horny, fistular, branched, forming dense tufts, three to four inches in 

 height ; branches alternate, spreading, subdichotomous towards the 

 * ' Quart. Jouru. Micr. Soc. Vict.,' i. (1879) p. 19. f H^id. 



