12 Mr. H. J. Carter on the Suhsj)herous Sjwnges. 



it, leaving the " pores" and " intermarginal cavities " of Dr. 

 Bowerbank for subsequent explanation. 



In my description of the ^' Ultimate Structure of Sjjongilla " 

 (Annals, 1857, vol. xx. p. 21), I have shown that the mem- 

 brane-like sarcodal expansion in which Dr. Bowerbank's 

 '^ pores " are situated, is composed, like the rest of tlie animal, 

 of a congeries of polymorphic sponge-cells, and that thus 

 these " pores " can be extemporized or closed in any part of 

 this structure that occasion may require. Hence Dr. Bower- 

 bank's term of " dermal membrane " does not give an adequate 

 idea of the real nature of this develoj)ment. Indeed it would 

 be out of place, as it is out of character, to expect in the ever- 

 changing, polymorphic, sarcodal substance of these primitive 

 animals anything to which the term " membrane," as it is 

 used in anatomical description for the higher animals, could 

 be applied ; and it was on this account that, in the '■ Annals ' 

 of 1856, I proposed the term "pellicula" for the surface of 

 sarcodal structures, this having previously been suggested by 

 Mohl for the consolidated surface of material which has no 

 distinct enclosing membrane, and by Dujardin, who likens 

 it to the film which occurs over " flour paste or glue when 

 allowed to cool in the air." 



I am aware that I have misapplied the term "membrane" 

 myself, as regards SjJongilla^ in the paper to which I have 

 alluded ; but that is no reason why I should repeat it here. 

 In this paper, also, I have used the term " apertures " for the 

 extemporized holes in the sarcodal expansion covering the 

 sponge, and the terms " afferent" and " efferent" for the in- 

 current and excurrent systems of canals respectively which 

 are hollowed out in the parenchyma of the body, and I shall 

 continue to use these terms under the same signification. It 

 should, however, be remembered that while the efferent canals 

 form a distinctly arboritic system, the afferent ones appear to 

 be only passages of intercommunication between the exterior 

 of the sponge and its areolar or vacuolar cavities, and between 

 the areolar cavities themselves. For the more ultimate struc- 

 ture of the parenchyma in Sjwngillaj see ' Annals,' L c. 



From the " pores " (that is to say, my " apertures ") let us 

 follow Dr. Bowerbank on to his " intermarginal cavities," 

 wliich, at p. 101, Brit. Spong. vol. i., are thus described : — 

 " They arc in form very like a bell the top of which has been 

 truncated. They are situated in tlie inner portion of the der- 

 mal crust, the large end of tlie cavity being the distal, and tlie 

 smaUer end the proximal one. The open mouth or distal end 

 of the cavity is not immediately beneath the dermal mem- 

 brane. There is an intervening stratum of membranes and 



