RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 367 



Pinacocystis rubicunda, Hertwig et Lesser .^ (Fig* l^-) 



Although the object of the present resume is to bring 

 before the readers of this Journal the recently discovered 

 rhizopodous forms of the freshwater only, that which Hertwig 

 and Lesser describe under this name, found in sea-water 

 from Cologne, comes so close to those characteristic of the 

 former element, it could not properly be omitted. And 

 this the more especially as the authors call to mind that the 

 representatives of the Heliozoa known to appertain to the 

 sea are but few, hence tending to indicate the erroneousness 

 of the ordinary appellation " Freshwater Kadiolaria," and to 

 show how little it accords with the geographical distribution 

 of the Heliozoa to regard them as a group in the course of 

 " natural selection " as it were halting behind the marine 

 forms. In this point of view Heterophrys marina occurring 

 in fresh water, as mentioned, is also interesting. 



This form as regards the "skeleton" might be compared 

 toan Acanthocystis, wi/Aow/ " spines," however, but with the 

 "basal-plates" appertaining to that genus, the skeleton 

 being formed of giobularly arranged round tablets, without 

 appendages. The structure of the body-mass agrees with 

 that of that genus — the absence of demonstration of contrac- 

 tile vacuoles the authors suppose might have been due to 

 unfavorable examples ; the peculiar sienna-brown colour of 

 the granules would only at best be of specific value. The 

 pseudopodia are less numerous and shorter than in the species 

 of Acanthocystis, but they otherwise resemble. In fact, the 

 authors felt inclined to embrace this form in that genus 

 (slightly expanding, of course, its limits), and refrained 

 mainly on account of the fact that the name necessarily 

 conveys that the skeleton is composed of spines. 



Pinaciophora fluviatilis, Greeff.^ (Fig. 5.) 



(found as yet by the author only in freshwater streams), in a 

 generic point of view comes very close to the foregoing, 

 though, no doubt, it is quite a distinct species. It is charac- 

 terised like the preceding by the possession of peripheral 

 plates, closely arranged in a hollow-globular manner ; but 

 here these are not round and flat, but of a compressed oval 

 figure with pointed ends, thus broader in superficial view 

 than when seen towards the " equator " of the rhizopod ; 

 they are, moreover, according to the author, perforated by 

 numerous fine foramina, appearing as fine lines running 



• Loc. cit., p. 209, t. iv, f. 5. 



=> ' Schultze's Arcbiv,' Bd. xi, p. 26, t. i, ff. 15, 16, 17. 



