Prof. All in an on the Hydroid Zoophytes. 3G9 



II. Clava discreta, nov. sp. 



In August last I obtained, upon the under surface of a stone 

 near low-water mark, upon the shore of one of the small rocky 

 islands of Orkney, a species of Clava which may be defined by 

 the following short diagnosis : — 



Char. — Polypes not grouped, into clusters, but distributed at 

 intervals upon a branched creeping stolon. 



Clava discreta differs from C. multicomis chiefly in the pecu- 

 liar development of the stolon, which consists of a branched 

 creeping tube, invested with a distinct polypary, and sending 

 up, at intervals of from about | to i an inch, very short free 

 simple stems whose height scarcely exceeds the diameter of the 

 stolon, and from whose summit the polypes emerge. The 

 polypes are thus widely separated from one another, instead of 

 being collected into clusters as in C. multicomis. They are of a 

 light brown colour, and are also smaller than those of C. multi- 

 comis, scarcely exceeding \ inch in height. In other respects 

 they closely resemble them. The tentacula are about twelve in 

 number, and the sporosacs are grouped in two or three clusters 

 just behind the proximal tentacula. 



The only specimen of this species I obtained was attached to 

 the dead stolon of some other zoophyte, probably a Coryne, which 

 it accompanied in its ramifications over the under surface of the 

 stone on which it grew. 



III. Dicoryne stricta, nov. gen. and sp. 



The subject of the present note was dredged at Orkney in 

 August last, in water of about three fathoms depth. It invested, 

 an old Buccinum undatum which contained a Hermit Crab, and 



the Medusa of Laomedea dichotoma, which I carefully examined with 

 regard to this point, are constructed precisely on the plan of the sporosacs 

 in Clava, Hydractinia, &c. These sporosacs must he viewed as special 

 zooids representing one term in the " alternation of generations " of the 

 individual. Just so must the reproductive hodies (sporosacs) which bud 

 from the radiating canals of the Medusa of Laomedea dichotoma be regarded 

 as special zooids, and as representing a term in the life-series of the zoo- 

 phyte. 



In Eudendrium ramosum, for example, we have therefore this series re- 

 presented by two terms : — 



[Ovum] polype, medusa ; 



while in Laomedea dichotoma it is represented hy three : — 



[Ovum] polype, medusa, sporosac. 



In the Eudendrium, the series stops with the production of a sexual 

 zooid in the form of a Medusa ; in the Laomedea it goes on through the 

 non-sexual Medusa-bud until it rinds its termination in the sexual sporosac- 

 bud of the latter. 



Ann. $ Mag. N. Hist. Ser. 3. Vol. iv. 24 



