Organisms Consisting of One Cell 239 



Intimately connected with the network of sarcode situ- 

 ated within the substance of the shell and on its surface is 

 the wonderful pseudopodial system, i.e., the system of in- 

 numerable filamentous, anastomosing, expanding, withdraw- 

 ing, and shifting strands of living material. As is well 

 known, at least for many Rhizopoda, tlie pseudopodial sys- 

 tem is nutritional in function. First of all, the pseudopo- 

 dia are prehensile organs and operate in much the same way 

 and apparently with as great effectiveness as the corre- 

 sponding organs of higher animals. By means of them the 

 animals seize their prey consisting of living micro-organisms. 

 In some species the seizure is accompanied by a stunning 

 and paralyzing action. After capture the food is, in many 

 species, transported by the grasping organs through the 

 mouth of the shell and into the deeper portions of the sar- 

 code there to undergo digestion. But in some groups the 

 nutritional office of the pseudopodial system goes much 

 farther than the mere procurem.ent of food. Digestion, and 

 so of necessity circulation in part, are performed by the 

 same system. Calkins ^ mentions the Reticularia particu- 

 larly as Rhizopods whose digestion is thus performed. What 

 could be more far-fetched and distracting of attention from 

 the true nature of the animals, than to call organs that per- 

 form all these functions "feet," false feet, or feet of any 

 other kind.^ 



The locomotor appendages of many animals are brought 

 into the service of the nutritive function ; and in such ani- 

 mals, as many of the Crustacea, where this change of func- 

 tion has gone so far as to divert the organs entirely from 

 their original office and transforai them both structurally 

 and functionally into mouthparts, comparative anatomists 

 never think of still lumping them all together as locom,otor 

 organs. In no higher animal whatever, so far as I know, 

 has conversion of the locomotor into nutritional organs 

 gone so far as to make them not only food-seizing but food- 



