RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 369 



it is the same in kind as that of Heterophrys T fancy must 

 be true ; it is more mobile, more homogeneous-looking — 

 that is to say, less striate and granular-looking — than in that 

 genus ; but the one great distinction seems to be its possess- 

 ing spicules which are absent in Heterophrys (leaving out of 

 view the peripheral capillary processes claimed as " spines " 

 by Hertwig and Lesser). And with what I venture to hold 

 some amount of contradiction, after having defined the 

 heliozoan as composed of but one stratum only, surrounded by 

 a skeleton formed of numerous spicules, these authors proceed 

 to speak of the sparing protoplasm-medium cementing and 

 holding together the pieces of the skeleton. In describing 

 R. elegans they say that ^' between the spicules they were 

 able to perceive, especially after adding acetic acid, sparing 

 granules, and they regard these as slight traces of pro- 

 toplasm originating from the pseudopodia, and combining 

 the loosely disposed skeleton pieces." This seems, I venture 

 to hold, to be yielding the question in dispute, and I should 

 suppose the admissions capable of being extended to other 

 genera. If this, after all, undeniably soft-connecting medium 

 owes its origin to the pseudopodia, they at all events pass 

 up from the central inner body-mass through and through 

 this outer spicule-carrying region, appearing during the 

 whole distance quite sharply marked and without any evidence 

 of becoming gradually softened or dissolved, or in fact at 

 all modified in nature. In either R. viridis or R. elegans 

 when an example is first placed on a slide, one at first sees 

 the outer spicule-bearing region quite flaccid as it were, and 

 the contained spicules " tossed " irregularly, but with a 

 great tendency to lie very much in a tangential direction ; in 

 a short time, when the organism begins, as one might sup- 

 pose, to recover the shock of the transfer from the " collect- 

 ing-bottle " to the slide, this outer region (in R. viridis, to 

 my eye, as well, offering a more or less evident degree of 

 very light purplish-brown tint) begins to stand off in a number 

 of radial somewhat conical prominences, and the spicules 

 become more or less tilted on end, and masses of them 

 become piled in conical heaps, and clustered about and as it 

 were, more or less, lying obliquely against certain of the 

 pseudopodia, whilst in R. elegans they assume more and 

 more of the curious festoon-like arrangement seen in that 

 species. All this they could not do spontaneously, one must 

 suppose, but rather they obey the innate movement of the 

 medium in which they are immersed. Doubtless the elon- 

 gation of the pseudopodia must and does contribute to effect 

 this, by assisting to carry upwards the piles of spicules 



