PBOTOZOA. 



blood-cells of man, from which they cannot be distinguished ; 

 but it is doubtful whether many of them can be any thing more 

 than the earlier stages of other organisms. A sort of carapace 

 or discoid shell is common to Arcella ; in Difflugia it is replaced 

 by a shell formed by foreign particles agglutinated together. 



The limits of this order are undecided. Schmarda unites 

 Amoebidae with Acinetidae to form his order " Thalamia, or Bhi- 

 zopoda nuda." Von Hayek includes in it the three families of 

 Amcebidaj, Arcellidae, and Actinophryidse ; Glaus places the latter 

 in the Radiolaria, but Hack el, followed by Mivart, excludes it. 



The Heliozoa are mostly freshwater organisms, sometimes pro- 

 vided with a siliceous skeleton of detached radiating spines, or 

 with a hollow perforated globular shell (Clathrula], Except 

 Actinophryidse, they appear more nearly related to Radiolaria 

 than to Arnoeboidea. 



Pelomyxa is an " amoeboid organism " " spreading over the 

 bottom of stagnant pools." 



The normal Amcelooidea include two families : 



Amcebidce. 

 Amoeba. 

 Corycia. 

 Podostoma. 



ArcelKtUt. 



Arcella. 



Euglypha. 



Difflugia. 



The Heliozoa include three families. Actinophrys sol is the 

 well-known "sun-animalcule" of microscopists. Actinophryidae 

 constitute the order Phloeophora of Carus. Magosphcera is re- 

 markable in that in its life-history it presents four independent 

 forms ; the first morphologically represents an egg, the second is 

 a Volvox-form, the third is a ciliated Infusorian, and the last appa- 

 rently an Amoeba. It was discovered on the Norwegian coast by 

 Hackel, who considers it the representative of a distinct group 

 (Catallacta) linking together several of his Protista; but Huxley 

 thinks it should form a "subdivision" of Infusoria ciliata. 



Actinopliryidce. 

 Actinophrys. 

 Actiuosphagrium. 

 Ciliophrys. 



Acanthocystida. 

 Acanthocystis. 

 Rhaphidpphrys. 

 Heteropurys. 

 Cystophrys. 



ClathrulinidcK* 

 Clathrulina. 

 Hyalolampe. 

 Hedriocystis. 



Magosphasra. 



