CLASSIFICATION 49 



that move by pseudopodia during the great part of tlieir 

 active life), and the FLA(iELLATA in the widest sense, are 

 not easy to split up ; lor many of the former have flagellate 

 reproductive cells, and many of the latter can emit pseudopodia 

 with or witliout the simultaneous retraction of their flagella. 

 The Eadiolapja are well defined by tlie presence in the 

 body plasm of a central capsule marking it off into a 

 central and a periplieral portion, the former containing the 

 nucleus, the latter emitting tlie pseudopodia. Again, on the 

 other hand, we find that we can separate as Flagellata in the 

 strict sense the not very natural assemblage of those Protista 

 tliat have flagella as their principle organs of movement or nutri- 

 tion during the greater part of their active life. The remaining 

 groups (which with the Eadiolaria compose the Sarcodina of 

 Blitschli), are the most difficult to treat. The Ehizopoda, as we 

 shall limit tliem, are naked or possess a simple shell, never of 

 calcium carbonate, have pseudopodia that never radiate abundantly 

 nor brancli freely, nor coalesce to form plasmatic networks, nor 

 possess an axial rod of firmer substance. The Foraminifera 

 have a shell, usually of calcium carbonate, their pseudopodia 

 are freely reticulated, at least towards the base ; and (with the 

 exception of a few simple forms) all are marine. The Mycetozoa 

 are clearly united by their tendency to aggregate more or less 

 completely into complex resting-groups (fructifications), and by 

 reproducing by unicellular zoospores, flagellate or amoeboid, which 

 are not known to pair. The Heliozoa resemble the Eadiolaria 

 in their fine radiating pseudopodia, but have an axial filament 

 always present in each, and lack the central capsule ; and are, for 

 the most part, fresh- water forms. Finally, the Pkoteomyxa 

 forms a sort of lumber-room for beings which are intermediate 

 between the Heliozoa, Ehizopoda, and Flagellata, usually passing 

 through an amoeboid stage, and for tlie most part reproducing by 

 Ijrood-formation. Zoospores that possess flagella are certainly 

 known to occur in some forms of Foraminifera, Ehizopoda, 

 Heliozoa, nnd Eadiolaria, though not by any means in all of 

 each group.^ 



1 See E. R. Lankester, art. " Protozoa " in Eucycl. Brit. 9tli ed. (1885), reprinted 

 with additions in "Zoological Articles." "We cannot accept liis primary division 

 into Cortieata and Gynmoniyxa, which would split up the Flagellata and mark off 

 the Gregarines from the other Sporozoa. 



VOL. I E 



