200 Prof. H. James-Clark on the Spongias ciliatse 



of momentaiy cliange. Unless it be by means of the vibra- 

 tions of the flagellum, there is no other immediate agent 

 which can be supposed to move the body up and down in its 

 sheath. There is no visible movement in itself, like creeping, 

 to be observed ; and moreover the body progresses so quickly, 

 Avhen changing its place in the calyx, that it becomes evident 

 that it is not due to any reptant mode of transposition. When 

 withdrawn (tig. 38) into the basal tapering portion of its calyx, 

 the collar {b) does not extend beyond the rim (c^) of the latter, 

 but, on the other hand, the body occasionally moves so far in 

 the opposite direction (fig. 39) that nearly the whole of the 

 collar (b) projects outside of the dormitory. 



The fiageUum is a delicate filament which arises from the 

 axial point of the front, and projects a short distance beyond 

 the edge of the collar. It presents a constantly undulating 

 aspect, and vibrates from base to tip. 



The mouthy we are obliged to presume, as we did in regard 

 to Codosiga, lies somewhere about the base of the flagellum. 

 Abundant digestive vacuoles were observed, as well as loose 

 particles of food, in various parts of the body ; but at no time 

 were we so fortunate as to see the introception of nutritive 

 material or the ejection of fgecal matter. 



The contractile vesicles icv) are two in number. They lie 

 between the second and posterior thirds of the body, usually 

 on ojoposite sides, and close to the surface. In aspect and rate 

 of systole they resemble those of Codosiga jpulcherrima^ but 

 they are a little smaller in proportion to the size of the animal- 

 cule. Sometimes the protean changes of the body are so ex- 

 tensive as to throw the two vesicles into a line with each other 

 in an antero-posterior direction ; but they hold this position 

 only temporarily, and soon return to their normal relations. 



The calyx (c c' c^) has the general shape and proportions 

 of a champagne-glass, and appears to be hollow to the very 

 bottom {&) of its pedicel-like inferior third. Anteriorly it is 

 truncate, smooth, and flares (c^) quite strongly. About the 

 middle it bulges very sensibly, and thence tapers gradually 

 into a slender posterior third (c^), but expands again slightly 

 as it terminates upon its place of attachment. It is colourless, 

 excessively transparent, and exhibits considerable flexibility 

 under the movements of the body, apparently having the con- 

 sistency of a mere film. 



§ 8. Salpingoeca marina^ nov. sp. (PI. VI. figs. 28-32^) 

 The remarkable generic resemblance of this species to Codo- 

 siga has already (p. 193) been commented upon. It is very 

 connnon, especially upon the marine Hydromedusa Dynamena 



