46 Proceedings of the Royal Physical Society. 
derm with which it and the scleroderm were covered, and 
which could only be removed by directing a strong stream 
of water against it. 
(5.) Coryne ferox (n. sp.), T. S. W. 
Polypary creeping. Polyp-stalks single, smooth. Ten- 
tacles, thick, short, having the capitate cluster of 
thread-cells scarcely larger than the width of the 
tentacle. Medusoids developed beneath the tentacles 
similar to those of C. decipiens. 
This Coryne resembles C. decipiens (Dujardin) in the 
shape and mode of development of the medusoids, but it 
differs from that zoophyte in its more robust and clumsy 
habit. The tentacles of C. decipiens are long, tapering, 
and capped with large bulbs of thread-cells. Those of C. 
ferox are short, nearly of equal thickness throughout, and 
though they are surmounted with a cluster of thread-cells, 
the thread-cells are so few in number, that the tentacles can 
scarcely be called "capitate." A delicate epidermis of coUeto- 
derm passes over the whole body and tentacles of the polyp, 
which causes it to assume a dirty appearance, as it often 
serves to support a downy growth of very minute algse. C. 
decipiens is the hardiest of all the hydroidse ; I have known 
a colony of it to live for six years in captivity, whereas C. 
ferox seldom survives more than a few days after having 
been removed from the sea. 
III. On Ophrjdium versatile, Ehr. By W. R. M'Nab, Esq. 
The Ophrydium versatile is one of the most curious of all 
the infusoria, occurring as it does in large gelatinous masses of 
a greenish colour, which are sometimes adherent to the stems 
of aquatic plants, but often free, and floating on the water, 
like masses of frog's spawn, for which it has been mistaken. 
It is found in considerable quantity in several ponds near 
Edinburgh ; and from its abuu dance in the Botanic Garden 
pond, the observations here recorded were made, an abundant 
supply being at all times at hand. The gelatinous masses 
contain great numbers of the individual Ophrydia, which 
