Eev, T. Hinck^ on the Production of Gonozooids. 459 



LTI. — O71 the Production of similar Gonozooids hy Hydroid 

 Polypes belonging to different Genera^. By the Rev. Thomas 

 HiNCKs, B.A. 



[Plate IX. figs. 1 & 2.] 



In the course of the past summer I have had the opportunity of 

 studying at Tlfracombe the reproduction of the Stauridia producta, 

 a small Tubularian Zoophyte, which abounds in rock-pools and 

 under ledges near the base of the Capstone. It was first cha- 

 racterized by Dr. Strethill Wright (Edinb. New Phil. Journ., 

 N.S., for April 1858) ; but he did not observe the reproductive 

 bodies. It has been my good fortuae to meet with one or two 

 polypes on which they were present in an advanced stage of 

 development, and I am thus enabled to complete the history of 

 the species. 



My principal object, however, in this paper is to put on record 

 the remarkable fact that the gonozooid of the Stauridia producta 

 is identical with that of the Coryne eximia {Allman)j a member of 

 a distinct genus. 



Stauridia is nearly allied to Coryne, but is distinguished from 

 it by having tentacles dissimilar in character. The upper, which 

 are arranged in one or more whorls, are furnished with globular 

 tips, as in Coryne, while the lower, which form a single verticil, 

 are filiform. The former are armed with thread-cells, and en- 

 dowed with vigorous percussive power, and constitute offensive 

 and prehensile instruments ; the latter are rigid, and furnished 

 with palpocils, and seem to act as tactile organs only. 



The S. producta is a small, creeping, unbranched form ; the 

 C. eximia is branched, and attains a considerable size. Yet of 

 the life-series of these two Hydroids, thus dissimilar in general 

 character, one term is identical. The free reproductive zooids 

 of each are, at the time of detachment, undistinguishable from 

 one another. A strictly analogous fact would be the production 

 of flower-buds absolutely identical by two plants of different 

 genera. 



In his account of Coryne eximia (^Annals' for August 1859), 

 Prof. AUman has remarked on the similarity of its gonozooid to 

 that of another species of the same genus — the Coryne Sarsii of 

 Lovenf. He was unable to indicate any character which could 

 be "justly considered as pointing to a specific distinction be- 

 tween the two Medusae," though he admits that " a more exact 

 comparison with the living animal " might probably result in 

 the detection of differences not then apparent. Dr. Wright, 



* The substance of this paper was communicated to the Natural-History 

 Section of the British Association, at the late Cambridge Meeting, 

 t The Syncoryna decipiens. of Dujardin, 



