Mr. W. Thomson on some British Zoophytes. 443 



as the mass never loses its definite shape, and never increases in 

 size beyond a certain point. The propagation of this species by 

 means of planulae has been most correctly described by Sir John 

 G. Dalyell (Rare and Remarkable Animals of Scotland, vol. i. 

 p. 224). The planulse appear to be free buds developed from 

 the base of the hydra, escaping into the cavities of the areolar 

 matrix. 



The free extremity of the tube-cell is provided with a valve- 

 like operculum, which closes on the retreat of the polyp and after 

 its death. 



The species which I am about to describe, and which I shall 

 call Reticularia immersa, differs from Coppinia and approaches 

 the other Sertularians in having its polyp-cells springing from a 

 common horny tube. This tube is in the form of an anasto- 

 mosing, investing network, and is immersed in a homogeneous 

 horny secretion, from which the minute, curved polyp-cells, dif- 

 fering little in calibre from the common tube, stand out. 



The propagation of this species has not been observed. 



Reticularia, n. g. 



Animal, a Sertularian polyp of a greenish colour, with nume- 

 rous smooth, solid tentacula ; Very minute. Polypidom, a para- 

 sitical investing network of horny tubes, immersed in a homo- 

 geneous horny crust. Polyp-cells short projections of the net- 

 ted tubes, arc-shaped, with circular, patulous orifices without 

 opercula. 



jR. immersa, n. s. 



I have found this species pretty frequent at Newhaven, usually 

 investing Sertularia abietina. Aberdeen, P. Forbes, Esq. 



Coppinia arcta appears to have but a slender title to a position 

 among the CampanulariadcB, where Dr. Hassall originally placed 

 it, and some of its allies seem to dwell among them with as little 

 cause. The four Laomedem have undoubted right, and Campa- 

 nularia lacerata, which has been shown by Mr. Hincks to be refer- 

 able to this genus (Hincks in lit.) ; and so have Campanularia 

 volubilis, C. caliculata and C. Integra. 



Mr. Hincks has however shown that the so-called Campanu- 

 laria syringa is a true Sertularian ; its near ally C. minutissima 

 (Hincks) may probably accompany it. C. dumosa appears to be 

 nearly allied to Coppinia ; the connecting link Reticularia pos- 

 sessing much of the habit of C. dumosa united to the investing 

 crust of Coppinia. 



Probably, when their reproductive processes have been more 



29* 



