33 



sometimes Difflugiee loaded witli chlorophyll granules. 

 Raphidiophrys viridis sometimes, but it is rarely, shows some 

 colourless granules. I cannot but think, therefore, that A. 

 pallida is only a colourless, not at all uncommon state, of 

 A. turfacea. 



But as regards another form (not named) referred to by 

 Greef I would, indeed, very deferentially think he had far 

 better ground to establish it as a distinct species. I mean 

 the form he gives in PI. XXVII, fig. 18. TJiis form seems 

 to be distinguished from A . turfacea by the want of the 

 shorter series of radial spines — by the longer series, less copi- 

 ously present, being, according to Greef 's account, immersed 

 to a certain extent within the periphery of the inner body — 

 and, further, by the outer sarcode region, here strongly pro- 

 nounced, being subdivided at the outer margin into a great 

 number of exceedingly delicate, linear, acute processes, the 

 pseudopodia passing, just as in A. turfacea, vight out through 

 the outer region afar into the water. This fringe-like sub- 

 division of the marginal or circumferential portion of the 

 outer sarcode-region strongly resembles that characteristic of 

 my Heterophrys myriopoda (see my PI. XVII, fig. 4). In 

 that form, however, there are no radial spicula like Acantho- 

 cystis. Further, judging from Greef's figure his form is of 

 a more olive-coloured green than A. turfacea. I do, there- 

 fore, venture to think this must really be quite distinct. 



Greef, moreover, names a further new form AcantJiocystis 

 spinifera, of all the described forms, coming nearest to my 

 A. Pertyana, but, as will be seen in the remarks following 

 the diagnosis of that species, under the head of Affinities and 

 Difi'erences, seemingly, indeed, quite a different thing there- 

 from. 



The following will, I think, serve as a diagnosis of the 

 new form occurring in this country : — 



Acanthocystis Pertyana (Arch.) . 

 (PI. XVI, fig. 1). 



Specific characters. — Radial spicula very short, shaft 

 comparatively thick, tapering, pointed at the apex ; pseudo- 

 podia very slender, in length about equal to the diameter of the 

 body, bearing minute granides passing up and doivn ; body 

 mostly colourless, but sometimes green when more or less loaded 

 with chlorophyll-gramdes. 



Measurements, variable ; diameter of body from ^ ,', „ to 

 fj-i-f^-, length of spine --V-ou to j ..\, „ of an inch. 



