28 



Further accounts of its structure internally are given by 

 Grenadier and by Greef in the papers already alluded to, 

 but they are open to confirmation, and it may, therefore, be 

 here useful as briefly as I can, to presently try to convey their 

 observations. 



The form described by Grenadier and called by him 

 AcantJtocystis viridis, is regarded by him as identical with 

 Actinojjhrys viridis (Elir.), but as distinct from A. turfacea 

 (Carter). Greef, on the other hand, considers he latter and 

 Grenadier's form to be identical, and truly none else but 

 Actino^jhrys viridis (Ehr.). I would myself still venture to 

 hold a different opinion, and regard it as not proven that 

 Acanthocystis turfacea (Carter), is actually the same as 

 Actinophrys viridis (Ehr.), That form is figured by Ehren- 

 berg as densely fringed by the pseudopodia, which are very 

 short, say not more than one third or one half of the dia- 

 meter of the body. Even assuming that the radial processes 

 are really siliceous spines (the true pseudopodia overlooked), 

 they are thus so far quite unlike either Grenacher's or Greef's 

 or our Irish form in these respects, for in these the spicula 

 are comparatively fine and long, the longer ones quite equal 

 in length to the diameter of the body (if not, indeed, longer), 

 not to speak of their occurring of two distinct lengths. In 

 fact, Ehrenberg's figure shows the radial processes only about 

 equal in length to the shorter series of spines of A. turfacea. 

 In the latter form, too, they are far less numerous and less 

 crowded — could be without much difficulty counted — they 

 do not form the dense fringe-like border shown by Ehren- 

 berg. Hence it appears to me to be still a matter of doubt 

 that Ehrenberg's Actinophrys viridis is trulythe same as Acan- 

 thocystis turfacea (Carter), or A. viridis (Grenadier), provided 

 the two latter forms are distinct ; until it should be proved 

 that they indeed are truly identical. Carter's name should for 

 the present, at least, and unless A. viridis (Ehr.) could be 

 })roved to be the same thing, maintain its currency. 



The observations of Greef on the form A. turfacea (Carter), 

 (A. viridis, Greef), are, as I shall now briefly try to narrate: 

 The body is of a globular figure, frequently densely filled 

 with green granules, shoAving apparent vacuoles, not pul- 

 sating. From the circumference of this globular body there 

 stand oif in a radial manner the closely posed siliceous spi- 

 cula, these of two lengths. The longer are hollow spines ex- 

 panded at the base in a discoid manner, and minutely forked 

 at the apex. These are said to be by Greef in length about two 

 thirds of the diameter of the body ; I myself think they mostly 

 attain in lenath as much at least as the full diameter of the 



