236 GElfEEAL HISTOET OF THE IK^FUSOEIA. 



other (by tearing to pieces a minute portion of the sponge under water in a 

 watch-glass), the isolated individuals may be seen to approach each other, 

 and apply themselves together in twos and threes, &c. and so on, until, from 

 a particle only discernible by the microscope, they assume the form of an 

 aggregate mass visible to the naked eye ; and such a portion, growing and 

 multiplying, might ultimately reach the size of the largest masses adhering 

 to the sides of the tanks at Bombay. They appear to belong to the genus 

 Am(eba of Ehrenberg." 



These changeable globules Mr. Carter, in the subsequent part of his 

 paper, designates Proteans, and states that they commonly resemble the Pro- 

 teus difflaens (Miiller). (" Notes of the species, &c. of the Fresh-water Sponges 

 of Bombay," Trans. Med. and Phys. Society, Bombay, 1847. Appendix.) 



In his more recent contribution on the freshwater Sponges, Mr. Carter 

 describes ceUs, capable of greatly and rapidly changing their form, endowed 

 \^ith considerable motile powers, and furnished each ^^dth an imdulating 

 locomotive filament (XXI. 5). These organisms he considers to be zoospcrms, 

 or the speimatozoa of Sponyilla. Speaking of one, he says — *' When its 

 power of progression and motion (of a serpentine creeping character) beguis 

 to fail, and if separated fi'om other fragments, it soon becomes stationary, and, 

 after a httle polymorphism, assumes its natural passive form, which is that of 

 a spherical ceU. Diu'ing this time the motions of the tail become more and 

 more languid, and at length cease altogether." On the other hand, it may 

 attach itself to some fragment, or to another cell, and " become indistinguish- 

 able fi^om the common mass ; and the tail, floatrag and undulating outwards, 

 is all that remains ^'isible." In these structures there is, therefore, polymor- 

 phism as in Rhizopoda, but no actual extrusion of pseudojjodes ; and the points 

 of agreement, after all, are realty accidental, and not demonstrative of a 

 structiu^al affinity. In them we have reproductive germs, which coalesce and 

 disappear as independent existences, whilst in the case of Amoeba each speci- 

 men is an independent individual, and is never seen to coalesce with others 

 mto a common or sponge -hke mass. 



Dujardin devoted a couple of pages to speak of this affinity between ^?>zo?6ce 

 and Sponges ; and Perty even goes so far as to make the latter a third class of 

 the Ehizopoda, intermediate between Arcellina and Amoebina, on account of 

 the calcareous, silicious, or homy spicula which occur in their compound 

 mass, and constitute a sort of skeleton. 



The affinity ^vith Sponges is traceable even in the case of the testaceous 

 Polytlialamia, as Prof. AVilliamson pointed out in 1848, and in a subsequent 

 memoir in 1851 {Trans. Mic. Soc.) thus enters on the question : — " Looking at 

 the structiu-e of the shell of the Orbicidina adunca, and esj)ecially at the large 

 orifices which communicate between its various cavities, we cannot fail to 

 observe that it is a reticulated calcareous skeleton, whose proportionate rela- 

 tion to the size of the soft animal has diff'cred but Kttle from that of the 

 sihceo-keratose network of many Sponges to the slimy substance "with which 

 they are invested." 



So Dr. Carpenter (Proc.Roy. Soc. 18.55), in his critical examination of Orbito- 

 lites, " places that genus among the lowest forms of Foramrnifera, and con- 

 siders that it approximates closely to Sponges, some of which have skeletons 

 not very unlike the calcareous network which intervenes between its fleshy 

 segments." AYith respect to this idea of Dr. Cai^penter, that they are allied 

 to Sponges, Mr. Jeifi'eys (same journal) would remark " that Polystomella 

 crispa has its peripheiy set roimd at each segment with sihcious spicula, like 

 the rowels of a spiu\ But as there is only one terminal cell, which is con- 

 nected A\ith all the others in the mterior by one or more openings for the 



