394 Royal Society : — On the Distribution of 



as it does not seem natural to suppose that the former, which is 

 so essentially an Entozoon, could have been descended from a stock 

 capable of assuming solid food iu the outer world. 



Dr. Carpenter unconsciously gives us the weight of his opinion 

 in the following quotations from his valuable work on the mi- 

 croscope. On page 449 he says, spealdng of Sphcerozomn, 

 "Towards the inner surface of this (the outer) coat are scattered a 

 great number of oval bodies resembling cells, having a tolerably 

 distinct membraniform wall and a conspicuous round central 

 nucleus, thus corresponding closely with the Grei/arina type." 

 I might mention in passing that, having frequently taken iu 

 the towTiig-net the unequivocal allies of I)ict>/ocha with sarcode 

 bodies identical with those of Sphcerozoum, I have no hesitation 

 in assuming Dicti/ocha itself to belong rather to the Thalassicolhdae 

 than to the group with which it is more usually associated. 

 This family is commonly included under the bead of Ehizopoda ; 

 and there can be no doubt that the generalization, irrespective 

 of that term, is a correct one ; but it is a stretch of transcendental 

 anatomy to speak of the existence of pseudopodia in any member 

 of it. The radiating branched filaments withui the dense external 

 investment of Thalassicolla nudeata are not extensions of the sar- 

 code body, like those of Gromia for example, but apparently act as 

 retiuacula, and as conduits for dialytic currents, which may account 

 for the phenomenon of cyclosis observed in some instances. 



Professor James-Clark, of Pennsylvania, appears to have satisfied 

 himself, at least, that there is a remarkable agreement of characters 

 exhibited between the Porifera and the Infusoria, wliich are 

 connected, as he endeavours to show, by a regular gradation of 

 animals. The derivation of the latter group of Protozoa from 

 the former, which I had myself assumed quite independently, is 

 therefore supported by that gentleman's researches. 



Even with our present advanced knowledge of the Infusoria 

 it is doubtful if we do not still include amongst them the larvae of 

 Twhellaria ; and, indeed, the passage from the one type to the 

 other would appear to be natural and easy. On the other hand, 

 tracing through such forms as Ncnurtes, Bonellia, and Priajndus, 

 Sijymicuhis will lead directly to the less-equivocal EchLnodermata ; 

 and here the series must wiud up ; for further evolution, though 

 perhaps possible, does not appear to have taken place. 



The existence of such low or simple forms of Eotifera as the 

 genus Asjilanchna, for example, would be favourable to the idea 

 that the JVoctilucidaj might have been the progenitors of that order 

 of beings. It is of course quite gratuitous, but convenient, at 

 present to assume that the IVoctducidfe would thus hold the same 

 relationship to the Polycystiua that the Infusoria appear to do to 

 the Porifera. However this may be, it is more certain that the 

 Eotifera are at the root of the annulose and articulate series. 



From the Eotifera, through the Amielida, \\e may thus trace 

 the development of the crustaceous and chiticous types of Arti- 

 culata like a dichotomous branch. 



