QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 99 



Beneden, who recently spent some time on the coast of Brazil, 

 had the intention of making a special investigation of the 

 Bathybian question, and his results have not yet been 

 announced. 



Development of the MoUusca. — The embryology of the 

 Mollusca is beginning to find students in Germany. In the 

 * Niederlandisches Archiv fiir Zoologie,' vol. i, part 1, is a 

 paper by Dr. Emil Selenka, the editor, on the "First Forma- 

 tion of the Embryo in Tergipes claviger,''' illustrated by a 

 plate. In part 2 the same author has a paper on " The 

 Primitive Layers of the Embryo in Purpura lapillus,^' also 

 well illustrated. Both these papers belong to the newer 

 embryology ; that is to say, the author occupies himself with 

 the exact following out of the origin and disposition of the 

 cellular elements of the embryo. In his paper on Purpura 

 Dr. Selenka proposes to distinguish two modes of formation 

 of the blastoderm — "epiboly" and " emboly." The former 

 is accompanied by the presence of a large food-yelk, and the 

 egg is consequently meroblastic, or partially so. The first 

 formative cells grow over the partially segmented or wholly 

 unsegmented coloured yelk. In emboly the egg is holo- 

 blastic, and a pushing in of the cells of the primitive blasto- 

 sphere takes place. 



Dr. Salensky, of Kasan, has a paper with several plates, 

 on ^' The Development of the Prosobranchiata," in ' Kolliker 

 und Siebold's Zeitschrift,' 4th part for 1872, which has 

 much interesting matter on the "Veliger" larval-form of 

 various genera, but does not deal with histogenesis. 



The Development of Gastropoda opisthobranchiata is the 

 title of a paper by Dr. Paul Langerhans in the same journal, 

 part 2 for 1873, in which some points in the early develop- 

 ment of Acera bullata, Doris sp., and ^olis peregrina are 

 shortly treated from the point of view of the germ-layer 

 theory. 



Development of Rotifera. — The paper by Dr. Salensky, of 

 Kasan, on " The Development of the Rotifer Brachionus 

 urceolaris ^'' of which we gave last year a brief notice, is pub- 

 lished in full, with a coloured plate, in ' KoU. und Sieb. 

 Zeitschrift,' 18T2. 4th part. 



Development of the Bryozoa. —Dr. Heinrich Nitsche, in the 

 same journal, has an interesting note apropos of Metschni- 

 koff's observations on the development of Alcgofiella. Nitsche 

 has made a detailed study of this at Leipzig, and we may 

 anticipate a memoir from him on the subject. Meanwhile 

 Professor Smitt points out that in relation to certain repro- 

 ductive processes he has been misunderstood by Nitsche, 



