Royal Physical Society. 169 



Postscript to Communication on Cydippe pomiformis. 



On the existence of Thread-Cells on the Tentacles of Cydippe. 



By T. Strethill Wright, M.D., &c. 

 In my description of the tentacles of Cydippe (see page 63), I stated that 

 their surfaces were crowded with minute thread-cells. 1 was therefore 

 surprised to find it remarked by Professor Huxley (Medical Times and 

 Gazette, June 21, 1856), that true thread-cells had not been observed in 

 the Beroida, to which class Cydippe belongs. At that time the Firth of 

 Forth was swarming with a small variety of Cydippe, distinguished by the 

 rufous colour which tinged the bases of the tentacular cirri. The am- 

 putated tentacles of this species adhered with extreme tenacity to bodies 

 applied to them. When examined under a power of 300 diameters, they 

 were seen to be so closely studded with small cells, that their surface had 

 a granular appearance. These cells were spherical, and opaque from the 

 presence of molecular matter in their interior. When ruptured by pres- 

 sure, they were found to contain a simple short thread, more or less closely 

 coiled in a spiral form. The application r 



of distilled water burst the cell-walls and \ /"> q) 



uncoiled the threads. In the annexed # || '{\ : :M S "j 

 sketch I have shown at 1, the thread- cells ~? rtf* " : - :i [<J 



burst by pressure ; at 2, the molecular 



matter evacuated from the cells, which is in constant motion ; at 3, the 

 threads uncoiled by distilled water. 



