246 ZOOPHYTES. 



Cluster or Social Ascidian Zoophytes. — Plates L.,LI., LIT. — 

 The definite figure, number, and arrangement of the parts, have enabled 

 naturalists to detach a few zoophytes from the general enumeration, ai^d 

 to unite them in lesser sections. 



One of these has been constituted by Dr Fleming, under the name 

 I 'rilheria, which other authors incline to preserve, as sufficiently expressive. 



This, in a more extensive sense, comprehends those zoophytes with 

 cells approximated in groups or clusters, inhabited by an ascidian hydra 

 with eight tentacula : to which may be conjoined some with similar tenants, 

 but numerously arranged in rows on the different inorganic parts. 



By a remarkable disposition of Nature, masses or clusters of animals 

 belonging to the same product are generated at considerable intervals, 

 without any intermediate channel obviously connecting them. 



But the more distant cluster, being of later evolution, and the cells 

 nearest to the preceding being the larger and more mature, affords some 

 presumption of the vital principle of the one being derived from the other 

 developed before it, and conveyed by a secret communication. 



Here the skeleton seems to participate more of the substance of that 

 of the Tubularia and of the Pedicellaria than of the skeleton of the Cel- 

 lularian race. 



As one leading feature of this section is the number of tentacula be- 

 longing to the hydra being definitely eight, the Imbricata, Cuscuta, and 

 Leitdicjeva, fall properly within it : and the same characteristic distinguish- 

 ing the Spinosa, will sanction its annexation. My observations on a few 

 of these, also with eight tentacula, are not sufficiently mature for a sepa- 

 rate paragraph. 



\ 1. Valkeria imbricata. — Plate L. — The naturalist in commemo- 

 ration of whose name this genus is instituted, was a clergyman of the 

 Church of Scotland, established at Moffat, a village in the county of Dum- 

 fries, celebrated for the medicinal wells in its vicinity. These have been 

 very long in great repute for alleviating various distempers, and are now 

 much resorted to, especially in the summer season. Having been sent 



