30 Proceedings of the Royal Physical Society. 



on a contractile stalk. Actinophrys, again, consists of a glo- 

 bular mass of sarcode, in which may be distinguished two 

 tissues : an internal one, which I shall call " endosarc," en- 

 veloped by an external tissue, " ectosarc." The endosarc is 

 dense, loaded with molecular matter and nutritive granules ; 

 the ectosarc transparent, and produced into tentacular ap- 

 pendages. Actinophrys has no mouth. Animalcules, seized 

 by the tentacles, are drawn to the surface of the body, the 

 soft sarcode of which becomes depressed, closes over them, and 

 envelops them. They sink into the endosarc, and are ab- 

 sorbed. The endosarc is the alimentary tissue; probably 

 also the reproductive tissue. The ectosarc exercises the 

 prehensile function. The tentacular processes of Actinophrys 

 are homologous with those prehensile processes of the " ec- 

 toderm " which I have described as existing in several classes 

 of aquatic animals, and to which 1 have given the term " pal- 

 pocils," a term which has lately been adopted by my friend Mr 

 Gosse, in his interesting paper on Sarcodyction catenata. 

 In Zooteirea, when expanded, the whole of the ectosarc is pro- 

 longed into long and exceedingly attenuated palpocils, until the 

 animal assumes the appearance of a globular brush of spun glass 

 mounted on a transparent stalk. When irritated, the animal 

 slowly contracts its stalk until the body is brought close to 

 the surface on which it is attached, and the palpocils are con- 

 tracted to a mass of little nodules (fig. 7, b). The stalk is homo- 

 geneous, and is, as are the palpocils, a process of the ectosarc. 

 A group of these animals form a very striking microscopic 

 object when seen by the dark field illumination, — two cones or 

 brushes of light appearing to issue from opposite sides of the 

 body of each, and to pass round it in opposite directions when 

 the mirror is moved. I have derived the name Zooteirea from 

 Zwoc and rg/'g£o<r, a star, or rather a constellation. 



3. Corethria Sertularia. (Figs. 8, 9, and 10.) 

 This remarkable animal has occurred plentifully during the 

 last few summers on the Sertularia pumila, which grows at 

 low-water mark near Granton. I have only found it in one 

 locality, at the extremity of the first ridge of rocks which 

 runs out into the sea west of the long breakwater. Although 



