% Mr. H. J. Carter on the " Collar " 



The cluster was then immersed in spirit and water ; and 

 after a few hours another minute portion, having been cut out 

 from one of the specimens, was torn to pieces in like manner 

 to the foregoing, and placed under the microscope, when the 

 cell again was distinctly seen, although dead, with its cilium 

 straight and, of course, motionless, the collar partially re- 

 tracted, and the body more or less filled with indigo (PI. II. 



Thus it was proved that in the siliceous sponges {SjwngiUa) 

 and in the calcareous sponges {Grantia compressa) the same 

 form of monociliated sponge-cell exists, which will, in both 

 instances, take in indigo when supplied with it under the cir- 

 cumstances above mentioned. 



Further, it follows that, as these cells do take in crude 

 material, they are as much the animals of the sponge as the 

 little Ascidians are the animals of the compound Tunicata, — 

 ex. gr. BotryUus polycyclus (PI. II. fig. 41), where the Asci- 

 dians are imbedded in circular groups {h) in a common tough 

 gelatinous mass (a), each Ascidian having an oral orifice on 

 the surface for the reception of food &c. (o), and an anal orifice 

 which empties itself interiorly [d] into a common cloaca (e), 

 finally opening by a circular hole, also on the surface, in the 

 centre of each group {f). 



Thus satisfied that this monociliated cell existed in both 

 classes of sponges, viz. in SpongiUa and in Grantia compressa , 

 I souglit for it also in living specimens of Grantia cih'ata, 

 Leuconia m'vea, and Clathrina sulphurea^ where it was equally 

 well represented. 



I then tried the siliceous sponges, viz. Isodictya sinndans^ 

 Hymeniacidon plumosa, Microciona atrosanguinea, Ch'ona 

 celata, &c., and might have gone further; but the fact of the 

 sponge-cell being only half the size in the siliceous (viz. 

 1 -6000th of an inch in diameter) that it is in the calcareous 

 sponges precluded my seeing any thing more than the cilia. 

 Of all these sponges that I have examined, the common 

 Isodictya simxdans seems to be the hardiest and best fitted for 

 this purpose ; but all that 1 can state respecting my examina- 

 tion of it amounts only to fancying that I saw the collar round 

 the base of the cilium in profile. 



However, as, when my eyes were younger, I had determined 

 it in Sponydla in the way mentionca (1. c), that is sufficient to 

 establish its existence in at least one of tlie siliceous sponges. 



As the monociliated cell in Grautia compressa somewhat 

 differs from that represented in Prof. James-Clark's figure of 

 it in Leucosolenia botryoidcs (/. c. ]il, 9. [pi. 6, ' Annals,' vol. i.] 

 fig. 41), it is desirable that I should describe it more particu- 



