MEMOIRS. 



Resume of Recent Contributions to our Knowledge 

 of "Freshwater Rhizopoda." Part II. Heliozoa 

 (continued). Compiled by Wm. Archer. (With Plates 

 XXI and XXII.) 



In accordance Avith the views held by Hertwig and Lesser 

 they include in the group Skeletophora several Heliozoan 

 species in which I myself do not recognise the presence of 

 such hard parts as could projjerly admit of being designated 

 as " Skeleton ;" suchj for instance, are Astro disculus, Greeff, 

 Astrococcus, Greeff, Chondropus, GreefF, and Heterojjhrys, 

 mihi. Now, as I cannot therefore, at least as yet, coincide 

 with those writers, I am prevented in this resume from fol- 

 lowing them in placing such forms in the group Skeletophora. 

 But although the series of forms in question are indeed as 

 yet regarded by myself as without " skeleton" in the strict 

 sense, still on the other hand they are manifestly in advance 

 of the three forms already referred to — Actinophrys and 

 Actinosphserium, with (if admissible as distinct from 

 Actinophrys) Ciliophrys (Cienkowski) — in the possession of 

 the distinct and considerably differentiated outer region, in 

 a sense, constituting " skeleton" for Hertwig and Lesser. 

 This outer coat without spicules or spines clearly seems to 

 place them apart on the one hand from the ilaked forms 

 and on the other from the truly skeleton-bearing. One or 

 other of two plans suggests itself to me to avoid this diffi- 

 culty — either we might call Actinophrys (with Ciliophrys) 

 and Actinosphserium Askeleta nuda and the group in ques- 

 tion Askeleta chlamydophora^ or we might allow the former 

 to remain Askeleta {they are incontrovertibly destitute of 

 any skeleton) and the latter to stand as an intermediate 

 group equivalent to the former as well as to the Skeletophora 

 proper (equally incontrovertibly provided with skeleton) 

 under the name Chlamydophora. 



But, further, it seems likely that the establishment of yet 

 another group may be called for to embrace those seemingly 

 Heliozoan forms which cover themselves round with a more 

 or less deep and more or less loose or compact, but apparently 



VOL. XVI. NEW SER. Z 



