204 Prof. H. James-Clark on the Spongiae ciliatfe 



in the neck (/) and disappears altogether in the collar (/;). In 

 its general aspect the body with its collar might be compared 

 to a wine-glass with a long stem and a globose pedestal. The 

 globose part is the posterior half of the body ; and the stem is 

 its neck, or anterior half, which tapers rapidly from the main 

 part to one-quarter or one-fifth its diameter, and then gradu- 

 ally widens to nearly double that thickness at its front, where 

 the collar is set on. The f)-ont is truncate, or rises into a low 

 cone, upon which the flagellum (f) is based. The posterior 

 half of the body usually fills the liottom of the calyx (c) ; but 

 the rest and the neck (/) stand off from it at a very appreciable 

 •distance. In this respect there is a marked difference between 

 this species and S. marina (§ 8) . In the latter we might say 

 that the body is suspended from the aperture of the urceolus ; 

 but in the former it rests on the bottom of the calycle. Not 

 unfrequently, however, the whole body of this species lies 

 loosely within its calyx (fig. 37). 



The collar {h) is an excessively hyaline, filmy membrane, 

 whose distal margin is so extremely delicate as to almost 

 defy detection with the highest powers. In the latter respect 

 it is a more difficult object of research than that of S. marina. 

 Generally speaking, it may be described as obconical, but with 

 greatly varying degrees of width. In this relation it agrees 

 perfectly with that of 8. marina, and therefore need not be 

 redescribed here. At its greatest height it equals that of the 

 body, and always terminates in a smooth edge. In plasticity 

 it is also equal to that of the marine species. In one instance, 

 when the animal was disturbed by a predaceous Rotifer, its 

 whole body quickly retracted, and the collar totally disappeared, 

 as if melted down with great rapidity, but soon after protruded 

 slowly, at first with a broad base (fig. 37^, b), and then rapidly 

 narrowed at the latter point and assumed its usual proportions. 



The flagellum [fl] differs from that of S. marina, both in 

 proportions and deportment. It is usually rigid, and projects 

 considerably beyond the collar when the latter is at its greatest 

 height. It has a decided arcuate figm-e, with a uniform thick- 

 ness throughout, excepting near the base, which tapers rapidly 

 from the low cone in the middle of the front. Its apex moves 

 with quite gentle spasmodic twitches, and the whole becomes 

 flexible (fig. 37^,_y?) when faeces are ejected or some unde- 

 sirable particle enters the area within the collar. 



The mouth was not actually seen ; but that it exists some- 

 where about the base of the flagellum was sufficiently demon- 

 strated by minute particles of food being seen thrown by the lat- 

 ter organ against the front, and rapidly disappearing there. The 

 a/iins (fig. 37, a) certainly opens within the same area, as parti- 



