HISTOLOGY OF HYDRA FUSCA. 
219 
On the Histology ^ Hydra fusca.^ By T. Jeffery Parker, 
B.Sc., Professor of Natural History in the University of 
Otago. 
The few observations I have to offer on this much-discussed 
subject are partly confirmatory of, partly supplementary to, those 
of foeinenberg f they present a certain agreement with those of 
F. E. Schulze;^ while they are, in great measure, distinctly con- 
tradictory 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 
connection with an endoderm cell. Kleinenberg, in teased spe- 
cimens, saw that the ectoderm cells tapered towards their inner 
ends, and that each ^vas continued into a simple or branched 
process, of precisely the same character as the fibres seen in sec- 
tions : 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 Kleinen- 
berg’s directions as to methods of preparation, came to the con- 
clusion 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 pro- 
jecting beyond it in either direction, 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. Any one working at Hydra for a week or two, 
and using various methods of preparation, might readily frame a 
* From the ‘ Proceedings of the Royal Society,’ No. 200,. 1880. The 
Plate there given is not reproduced. 
2 ‘ Hydra,’ 1872. 
^ ‘ Ueber den Bau u. die Entwicklung von Cordylophora lucustris,’ 
1871. 
■* “ Histologic de I’Hydre et de la Rucernaire,” ' Arch, do Zool. exp., 
t, V (1870), p. 309. 
