72 Prof. H. James-Clark on the American Spongilla 



Nat. Hist., July 1871) ; and we do not, tlierefore, feel called 

 upon to add more to it. 



The principal aim of this article is to furnish new material 

 in [>roof of the polyc('])halism of the >Spongia3, and particularly 

 iji regard to tlieir relation with tlie Protozoa flagellata. We 

 are liighly pleased to find that Carter has lately {ut suj)., July 

 1871) confirmed our earliest observations* as to the organiza- 

 tion of the collar-hearing monads of Leucosolenia, by an in- 

 vestigation of Grantia compressa. He has also accepted our 

 interpretation of tlie horn-like processes of the sponge-cell of 

 HpoiujiUa alha^ that they are the outlines of a membranous 

 collar in profile. 



We have now to bring forward a fourth example of a cras- 

 padote flagellate monad cephalid in a sponge. It seems to be 

 a Hpongilla ; but specifically, at least in its monads, it differs 

 from the l^jnglish forms. For convenience' sake we will call 

 it Hpoiujilla (irachnoidea^ from its resemblance to an in'Cgular 

 spider-welj. It lives in freshwater streams and ponds, usually 

 aljout the bottom of the stems of water plants, or wherever 

 there is consideraljle shade, apparently avoiding the light, as 

 we seldom, if ever, found it in open water. In size it varies 

 from a few inches to a half a line in diameter, of no definite 

 shape, and lias a uniform fuscous or yellowish-brown colour, 

 and is wra};})(!d about by a filmy, transparent, colourless enve- 

 lope (" «Vr/;e.s'^m^ ?//e?/iZ'7rm^^," Carter). The brown colour is 

 inherent to the interior mass, in which the grou}JS of monads are 

 imbedded ; in fact Ihe latter are themselves as strongly coloured 

 by brown granular contents. The " investing membrane " is 

 also slightly tinged with amber colour by the large and small 

 spicules which are imbedded in it. Excepting in very small 

 specimens, foreign matter is often so thickly spread over the 

 surface as to obscure the vi(;w and seriously interfere with a 

 corre(!t interpretation of the relation of parts. We have been 

 most fortunate in our endeavours with tlie miimter individuals, 

 which occasionally, we found, would allow a view through and 

 through their entire bulk, and of course left full opportunity for a 

 satisfactory study of the details of special parts without our re- 

 sorting to the dissecting-needles. Any one who knows by ex- 

 perience the intense contractility of the living sponge can 

 appreciate the advantage of not jjeing obliged to destroy and 

 sever parts of an organism from their natural relations. Pre- 

 mising that thus every thing has been studied " in place," 

 even to the details of tlie monads, we shall endeavour to de- 



* Memoirs Boston Soc. Nat. Hist. vol. i. 18(17, '' On tho Rpongiiu cili 

 I InAisinia flufrtillata;" Ann. & Mag. Nat. Ilisf., Feb., March, and A 



18(18. 



lataj 

 pril 



