ZOOLOGY. 301 



appears in the Annals and Magazine of Natural History for 

 February. 



The fresh-water Rhizopods, a favorite subject of inquiry, 

 have been studied with great care by Hertwig, Lesser, and 

 Biitschli. An abstract of their works has been given by 

 Mr. Archer in the Quarterly Journal of Microscopical Science, 

 the third part appearing in the January number. 



Barrois finds that the sponges of the different groups 

 studied by him present the same essential processes of de- 

 velopment, but that these stages appear in a different order, 

 and more or less modified by different circumstances, in the 

 different groups. This general mode of development, or 

 primitive cycle, does not seem to him to be a gastrula fixed 

 like a hydra, and of which the inner layer is ramified into a 

 gastro-vascular system, as Haeckel supposes, but a compact 

 mass composed of two layers, the exterior representing the 

 exoderm, the interior the union of an internal and middle 

 leaf. From the middle layer arise the spicules. The oval 

 gastrula becomes fixed by its posterior end, and then be- 

 comes flattened and irregular in form ; cavities then appear 

 in the endoderm, or innermost layer, which are lined with 

 the peculiar ciliated cells found in sponges; and the oscules 

 then appear, by which water enters and bathes the cavities 

 within. These observations of M. Barrois do not seem to 

 sustain Haeckel's views as to the relationship of the sponges 

 to the polypes, with which he unites them. 



While Mr. Carter continues, in the Annals and Magazine 

 of Natural History, his papers on sponges, a memoir by Pro- 

 fessor Haeckel forms the second number of his "Studies on the 

 Gastroea Theory." It contains, however, besides considerable 

 theoretical matter, many new facts regarding certain simple 

 sponges called Haliphysema and Gastrophysema. They are 

 so simple in organization as to bear considerable resemblance 

 to the gastrula form of sponges, which, it may be remem- 

 bered, consists of a two-layered hollow sac. It is illustrated 

 by six well-drawn plates. 



The commercial sponges of our southern coast have been 

 described and figured by Professor Hyatt in a lengthy mem- 

 oir published by the Boston Society of Natural History, in 

 which he describes the mode of fishing for them, as well 

 as the manner in which they are prepared for the market. 



