312 II. JAMES-CLAEK ON THE AFFINITIES OF SPONGES. 



to bring its tip in a line with the body. It is therefore altogether eccentric, but vet its 

 curve lies in the same plane relatively to the mouth and lip as that of its marine congener 

 Its length is about two and a half times greater than that of the body, and it scarcely if at all 

 tapers from one end to the other. It usually is held in a rigid attitude, except at the tip' 

 which is always kept in a rapidly gyrating state, accompanied frequently by spasmodic 

 incurvatures, when floating particles are thrown by it toward the mouth (m). Its flexibility 

 is exhibited during the frequent spasmodic retrocessions of the body (fig. 33 c ) in the same 

 way as in the other species, and the like remark applies to its action when assisting the lip 

 to force the food into the mouth. 



The mouth (to) opens in a slight hollow which lies between the base of the flagellum on 

 one side and the lip on the other, and therefore is concentric with the longitudinal axis of 

 the body. It very readily takes in quite large particles (fig. 33, to) of food, with the aid 

 of the mcurvatmg lip (lp) and the flagellum (fl), and immediately encloses them in a diges- 

 tive vacuole, or, more properly speaking, a hyaline envelope, within which they revolve for a 

 while with considerable rapidity. The anus (fig. 33, a) lies in the same hollow as the mouth 

 but further up on the base of the lip. That it is distinct from the mouth was frequently 

 demonstrated by the collection of large globular masses in the base of the lip, and some- 

 times further up, and their subsequent exit thereabouts. 



The two contractile vesicles (cr, cv,) form another very strong mark of distinction, since they 

 are not only double the number of that of B. gracilijm. but are also situated at the extreme 

 posterior end of the body. They are quite conspicuous, and appear to lie right and left of 

 the plane which passes through the lip, flagellum, and furrow. The systole of each alter- 

 nates with the other, and occurs from five to six times in a minute, but with nothing remark- 

 able in its action, unless it be that it operates more moderately than in Monas. 



The calyx (c) has, in its fully developed condition, about the same shape and proportions 

 as that of the marine form (figs. 34, 35), but like the body, it is much larger. In its younger 

 stages (figs. 33 a , 33 b , 33° c, c\) its aperture (c 1 ) almost closes when the body is retracted (fie 

 33"), and during the protrusion of the latter its rim (fig. 33 a , c') embraces it very closely ; so 

 that on the whole the calicle has an elongate ovate shape, with a narrowed, truncate, smo'oth 

 margin. During the undeveloped stages of the calyx, the pedicel (pd) is less than half its 

 length, and from that it varies down to little (figs. 33 % 33°, pd) or nothing; but when the 

 former is full grown (fig. 33, c), the latter (pd) is at least half as long as it. It is more 

 slender than that of B. graciUpes, and like the latter is attached to the base of the calyx 

 opposite the insertion of the retractor ligament (r). 



§ 5. Codon(eca, nov. gen. 1 (C. costata, nov. sp.) 



(Plate IX., fig. 36.) 



Of all the calyculate Flagellata, the species before us is perhaps by far the most beautiful 

 both in physiognomy and proportions. It is a marine form, and was found with Bicosceca 

 graalipes. Genencally it differs from Bicosceca (§§ 3 and 4) in having neither a basal, retrac- 

 tor muscle, nor lip, nor lateral longitudinal furrow, and by the attachment of its single 

 flagellum (/) to the central point of the front. From Salpingceca (§§ 7, 8, and 9) it differs 

 principally in not possessing a projecting collar or rim about the anterior end, but, as in 



i /cwSwr, a bell ; olieu, to inhabit. 



