NOTES AND MEMORANDA. 433 



nematocysts are flevelopccl, and a fairly well differentiated layer of 

 muscular fibres which run parallel to the long axis of the body. The 

 supporting lamella, in addition to the cells on its outer surface, which 

 Professor Allman regarded as neuro-muscular, has also cells on the 

 inner aspect which, as the Russian observer points out, are flagellate 

 endodermal muscle-cells ; in addition to these there are in the endoderni 

 outgrowths (blastostyles), which are conical in form and centripetal in 

 direction, and which consist of large cells containing bro\vn pigment 

 granules and giving off amoeboid processes and flagella ; by the aid of 

 these plasmatic jirocesses the cell is enabled to feed itself directly, 

 while the flagella serve as tactile organs. 



The blastostyles, which carry the gonophores, differ in structure 

 from the " body " in the feeble development of the subepithelial and 

 muscular layers, the latter indeed being altogether absent in young 

 blastostyles ; the supporting lamella has no projecting processes, and 

 the ectoderm varies in character with the age of the blastostyle ; just 

 below the supporting lamella there are large dark-coloured cells, 

 whence are developed the generative elements. 



In the foot the ectodermal cells are five or six times as long as the 

 ordinary cells, are coarsely granulated, and may be converted into 

 gland-cells, which secrete a strong chitinous outer layer by which the 

 whole of the foot is covered. The cells for the nematocysts are also 

 present in somewhat large numbers, while the muscular layer is absent. 

 The supporting lamella is without any outgrowths, and the endoderm 

 is of the ordinary type. 



The tentacles consist of muscular epithelial cells, such as were 

 first observed by the author in Hydra fusca, and have since been seen 

 by the brothers Hertwig in the Medusce, together with a supporting 

 lamella and a simj)le endodermal layer. In the capitular portion of the 

 tentacle four kinds of nematocysts may be observed, three of which 

 are sui^plied with tactile haii-s. Between the nematocysts there are 

 elongated pigmented cells, while the supporting lamella is highly 

 developed, and broken up into fibrillae which take a centripetal 

 direction. 



Tentacular structures (claspers) are found between the blastostyles ; 

 these serve for the attachment of the developing ova, and, though 

 structurally similar to the tentacles, differ from them in having the 

 ectodermal layer differentiated into glandular cells, which serve to 

 attach the ova. The statement of Allman that these structures function 

 in fertilization is not supported by M. Korotneff. 



In continuation of his researches, Korotneff* describes the de- 

 velopment of the gonoi^hores ; the large embryonic cells at the base of 

 the endoderm of the blastostyle become collected together at various 

 points ; this " agglomeration " passes through the ectoderm, and forms 

 an elevation on the surface ; the jDcripheral cells of this " gonogenetic 

 chamber " (Allman) become provided with refractive granules, which 

 form a covering for the egg. One of the cells of the collection 

 increases greatly in size and absorbs its neighbours; impregnation 



♦ 'Zool. Anzeiger,' ii. (1879) 187. 

 VOL. II. 2 F 



