hetioeen the Bpongiadce and the Foraminifera. 355 



But even here the sarcode lives in the cavities^ which may- 

 be easily seen to be but an extreme degree of what is ah-eady 

 foreshadowed in the chambers of less complicated forms of 

 Foraminifera, while its communication with the exterior is 

 through the minute holes mentioned. 



Thus, while the minute holes on the surface of the Forami- 

 nifera are fixed in form and size in a solid hard crust for the 

 egress of the pseudopodia, the minute holes on the surface of 

 the sponge (that is, the " pores ") are situated in an unfixed, 

 ever-changing, soft sarcode for the ingress of water bearing 

 the particles of food on which the species may subsist. In 

 short, one goes out to search for food with its bare pseudopodia, 

 after the manner of an Actinia, while the other draws it into 

 the interior of its habitation by the aid of currents of water 

 produced by cilia, after the manner of an Ascidian. It is to 

 the latter, I think, that we shall by-and-by find the sponges 

 passing through Schmidt's Gummine<x. 



The structure (not the forni) of Polytrema appears to have been 

 like that of Parheria and Lqftusia, Carpenter and Brady (Phil. 

 Trans, vol. clix. part ii. 1869, pis. 72-80) ; but I have nothing 

 to do with iho. fossil Foraminifera here. 



It might be stated that the boring-sponges have a segmented 

 form, like the Foraminifera, and that they often, in oyster- 

 shells, leave a concamerated chain of cavities. This is true ; 

 but still they also have their sjiicular skeletons, and the pa- 

 rietes of their chambers consist of those parts of the oyster-shell 

 which immediately suiTOund the chambers. Thus the sponge 

 does not form for itself a concamerated test. The polythala- 

 mous cavity is merely a " burrow." 



Hence when Hackel states, regarding SquamuUna scopuJa, 

 that he suspects it to be a very simple Myxospongia, which, 

 like Dysidea, forms for itself a skeleton of foreign bodies, but 

 in other respects has the simple structure of his Olynthus^ 

 while his Olyntlius primordialis (Monographic, Atlas, Taf. 1. 

 fig. 1) is at the foot of his whole system, I am natui-ally in- 

 clined to say, '"'■Ex uno disce omnes''^ ? 



Among the mounted specimens which Dr. Oscar Schmidt 

 generously sent to the British Museum are two bearing respec- 

 tively SquamuUna scojnda and the branched variety of this 

 species, under which is Avritten in his o-\ra hand " keine Spon- 

 gien," as well here as in his estimable work on the Sponge- 

 fauna of the Atlantic Ocean, p. 72, 1870. But Schmidt speaks 

 with the modesty of a bond fide naturalist, Hackel with the 

 infallibility of a Pope*. 



* In the arrangement which I have proposed for the sponges in the 

 British Museum, and whicli will of course apply to all others, I find that 



23* 



