440 Proceedings of the Eoyal Physical Society. 
which runs beneath the insertion of tlie lower rim of ten- 
tacles. The zoophyte has the power of changing its place. 
Description of Plate XVII. (Vorticlava proieus .} 
Fig. 1. — Vorticlava Proteus contracted. 
Figs. 2, 3, 4, 5. — Same in diiferent states of extension. 
Fig. 6. — Diagram of the tissues of the polyp of V. Proteus ; a a', colletoderm 
attached to snbtentacular ridge b ; c, ectoderm ; d, endoderm. 
(2.) Trichydra pudica. (Plate XXII.) 
This hydroid, which I have already described to the 
Society, was found completely covering a small shell from 
the " Fluke Hole." As its mode of reproduction has never 
been observed, I placed it in a small vessel of carefully-ex- 
amined sea-water, and exposed it to light, a mode of treat- 
ment which often induces the Hydroidae to assume their 
medusoid phase. After some time, two small medusoids 
were found in the water, but I was unable, by the most care- 
ful examination, to detect their mode of development, as no 
" gonophores" appeared on any part of the coenosarc. The 
connection of these medusoids with Trichydra is yet open 
to doubt, although I am convinced that no other zoophyte 
occurred on the shell, or in the water in which it was placed. 
Medusoid of Trichydra pudica f — Umhrella mitre-shaped, 
covered with minute thread-cells. Suh-umhrella with four 
lateral canals, destitute of ovaries or sperm sacs. Peduncle 
short, cylindrical, four cleft at the mouth. Tentacles four, 
short, with two or four intervening tubercles. Oolites 
absent, eye-specks absent. 
Descrii^tion of Plate XXII. [Trichydra pudica.) 
Fig. 1. — Polyp extended, showing the lax habit of the zoophyte. 
Fig. 2. — Polyp withdrawing itself when disturbed. 
Fig. 3.— Young Polyp. 
Fig. 4, — Polyp within its tube. 
Fig. 5.— Empty cell. 
Fig. 6. — Supposed medusoid. 
(3 ) On the Development o/Pycnogon Larvoe within the Polyps of 
Hydractinia echinata. 
In a communication made by Professor Allman to the 
British Association in 1859, entitled, "On a remarkable 
form of Parasitism among the Pycnogonidce," the author de- 
