RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 293 



olaria, as (most of all) Greeff has striven to show. They 

 then pass to the consideration what value the remaining 

 characteristics shared by the Heliozoa and Radiolaria in 

 common possess, and how far these may point out the two 

 classes as two groups, as it were, growing upwards from a 

 common root; and some striking common characteristics, 

 no doubt, do present themselves, the most prominent of 

 which are the general figure of the body and the form of the 

 skeleton. 



The sphere must be regarded as the fundamental form of 

 the Heliozoa (homaxial fundamental form — " homaxone 

 Grundform," Hackel), for the formation of a stipes in some, 

 pointing as it does, to a certain extent, to a differentiation of 

 a posterior fixed, and an anterior free, extremity, may be 

 regarded as but a secondary alteration, exerting no influence 

 on the figure of the skeleton or the body itself. Now the 

 same typically homaxial fundamental form holds good for 

 the Radiolaria. Even the divergent forms presented by the 

 Cystidae, Discidae, &c., may be referred to a differentiation 

 of the body-axis, only some degrees further carried from the 

 original typical globular fundamental form. 



The question follows how far this agreement of body-figure 

 points to affinities between the two groups, touching which 

 the authors, whilst remarking that inner organization and its 

 mode of development is generally admitted as of more import- 

 ance than external configuration, record their own opinionthat 

 they do not hold the view of any close affinity between them, 

 notwithstanding agreement in external form, and taking 

 into consideration their differences of inner organization. 



Just as little do they see reasons to subordinate the Heliozoa 

 to the Radiolaria as regards the formation of the skeleton. 

 No doubt there are in this regard parallelisms — thus Raph- 

 idophrys with Sphaerozoum, Acanthocystis with Acanthome- 

 tridae, Clathrulina with Ethmosphaeridae, — possibly (?) 

 Heterophrys with Spongodiscus, Still amongst Heliozoa 

 there are skeleton- forms not comparable with those of Radio- 

 laria — thus the globules of Pompholyxophrys (Hyalolampe) — 

 the plates of Pinacocystis. In Radiolaria the portions of the 

 skeleton for the most part lie partly or wholly immersed in 

 the body-sarcode, and even sometimes penetrate the central 

 capsule ; in the Heliozoa, urge the authors, they form a 

 globular envelope (Kugelmantel) , at some distance from the 

 superficies of the body, and whose individual pieces, as would 

 to them appear, are held together only by protoplasm- threads 

 " emanating from the pseudopodia." 



Tor myself I cannot still help thinking that there exists 



