1879.] 



On the Histology of Hydra fusca. 



Gl 



IX. " On the Histology of Hydra fusca." By T. Jefeery Parker, 

 B.Sc, Lecturer on Biology in Bedford College, London, 

 and Demonstrator in the Royal School of Mines. Commu- 

 nicated by Professor Huxley, Sec. R.S. Received Decem- 

 ber 11, 1879. 



{From the Biological Laboratory of the Royal School of Mines.) 



[Plate 1.] 



The few observations I have to offer on this mnch-discussed subject 

 are partly confirmatory of, partly supplementary to, those of Kleinen- 

 berg,* they present a certain agreement with those of F. E. Schulze,f 

 while they are, in great measure, distinctly contradictory of the later 

 researches of Korotneff . £ 



1. The Ectoderm and the Muscular Layer. — The layer of longitudinal 

 fibres between the ectoderm and the endoderm was discovered by 

 Kolliker, who believed that each fibre was in direct connexion with an 

 endoderm cell. Kleinenberg, in teased specimens, saw that the ecto- 

 derm cells tapered towards their inner ends, and that each was con- 

 tinued into a simple or branched process, of precisely the same 

 character as the fibres seen in sections : from this observation the 

 important conclusion was arrived at, that the fibres were in direct 

 continuity with the ectoderm cells, thus forming a sort of nascent 

 mesoderm. 



Schulze figures the elements of the middle layer as fusiform fibres, 

 with somewhat jagged edges. Korotneff, following Kleinenberg's 

 directions as to methods of preparation, came to the conclusion that 

 the ectoderm cells were expanded (elargie) at their inner ends, and 

 that each carried a fusiform refringent fibre, attached by its middle to 

 the enlarged base of the cell, and projecting beyond it in either direc- 

 tion, so that the cell appeared as a lateral appendage (annexe) of the 

 fibre, rather than the fibre as a prolongation of the cell. 



How M. Korotneff can have come to this conclusion as to the shape 

 of the ectoderm cells, it is rather difficult to imagine ; by any ordinary 

 method of preparation it is perfectly easy to satisfy oneself that the 

 ectoderm cells of the body are, as a rule, markedly distinguished from 

 those of the endoderm by the tapering of their inner ends ; and, in 

 good specimens, that these ends are continued into longer or shorter 

 filaments. 



The question of the exact relations of the fibres is by no means 

 so easy to decide. Anyone working at Hydra for a week or two, 

 * " Hydra," 1872. 



f " Ueber den Ban u. die Entwicklung von Cordylophora lucustris," 1871. 

 % " Histologic de l'Hydre et de la Lucernaire." " Arch, de Zool. exp ," t. v, 

 (1876), p. 369. 



