GENEEAL EEMAEKS ON THE EHIZOPODS. 5 



The soft mass of protoplasm, or sarcode, forming the essential part of 

 the body of all Ehizopods, has no internal cavity like the body-cavity of 

 higher animals, neither has it a mouth like the higher Protozoa, nor has it 

 stomach or intestine. Without trace of nerve elements, and without defi- 

 nite, fixed organs of any kind, internal or external, the Rhizopod, — simplest 

 of all animals, a mere jelly-speck, — moves about with the apparent purposes 

 of more complex creatures. It selects and swallows i,ts appropriate food, 

 digests it, and rejects the insoluble remains. It grows and reproduces its 

 kind. It evolves a wonderful variety of distinctive forms, often of the 

 utmost beauty, and, indeed, it altogether exhibits such marvelous attributes, 

 that one is led to ask the question in what consists the superiority of ani- 

 mals usually regarded as much higher in the scale of life. 



In this relationship. Dr. Carpenter remarks of the Ehizopods, "If the 

 views which I have expressed as to the nature and relations of their living 

 substance be correct, that substance does not present any such differentia- 

 tion as is necessary to constitute what is commonly understood as ' organi- 

 zation ' even of the lowest degree and simplest kind ; so that the physiolo- 

 gist has here a case in which those vital operations which lie is accustomed 

 to see carried on by an elaborate apparatus, are performed without any 

 special instruments whatever, — a little particle of apparently homogeneous 

 jelly changing itself into a greater variety of forms than the fabled Proteus, 

 laying hold of its food without members, swallowing it without a mouth, 

 digesting it without a stomach, appropriating its nutritious material without 

 absorbent vessels or a circulating system, moving from place to place with- 

 out muscles, feeling (if it has any power to do so) without nerves, propa- 

 gating itself without genital apparatus, — and not only this, but in many 

 instances forming shelly coverings of a symmetry and complexity not sur- 

 passed by those of any testaceous animals." * 



Through the motile power of the Rhizop'od, it projects or extends 

 portions of its protoplasm, which act as temporary organs of locomotion 

 and prehension, and it again withdraws or contracts them so that they melt 

 away in the mass and leave no trace of their previous existence. From 

 their function, the extensions of protoplasm have received tlie appropriate 

 name of pseudopods (Gr. pseudos, false ; pons, foot). These appear, in gen- 

 eral, in different kinds of Ehizopods, in the condition of threads of extreme 



* Introduction to the Study of tbo Foraminifera. Preface, vii. 



