150 PROTOZOA. 



of the lowest degree and simplest kind ; so that the physiologist has here a case in 

 which those vital operations which he is accustomed to see carried on by an elabo- 

 rate apparatus are performed without any special instruments whatever a little 

 particle of apparently homogeneous jelly changing itself into a greater variety of 

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

 agating itself without genital apparatus ; and not only this, but in many instances 

 forming shelly coverings of a symmetry and complexity not surpassed by those of 

 any testaceous animals." 



The fresh-water, shapeless, gelatinous mass is called the Amoeba, and it shows 

 a voracious disposition by seizing upon minute substances and appropriating them 

 to the nutrition of its own jelly. This it does by surrounding and inclosing the 

 food supply, which is retained until it is dissolved or the desired part appropriated. 



The lowest Order of Rhizopoda has received the name of Monera (mmeres, 

 simple), of which Prof. Haeckel says: 



" In a state of rest most Monera appear as small globules of slime, invisible, or 

 barely visible, to the naked eye, and at most about the size of a pin-head. When 

 the Moner moves, there are produced on the surface of the little slime-ball finger- 

 like processes, or very fine radiating threads, the so-called false feet, or pseudopods. 

 The latter are simple continuous processes of the structureless, albumen-like mass 

 of which the body consists. We are unable to perceive different parts in it, and 

 we can obtain direct proof of the absolute simplicity of the semi-fluid mass of albu- 

 men ; for, with the aid of the microscope, we can follow the Moner as it receives 

 its nourishment. When minute bodies suitable for food, as, for instance, small 

 particles of decayed organic bodies or microscopic plants and infusoria, accidentally 

 come into contact with the Moner, they remain hanging to the sticky surface of the 

 semi-fluid mass of slime, and here produce an irritation, which is followed by a strong 

 afflux from the slimy mass of the body, and they become finally completely inclosed 

 by it, or they are drawn into the body of the Moner by displacement of the sev- 

 eral albuminous particles, and there digested, being absorbed by simple diffusion 

 (endosmosis). 



"Just as simple as is the nourishment is the mode of reproduction of these 

 primitive beings, which one can not positively call animal or plant. All Monera 

 propagate themselves only in an asexual manner by self-division. When such a 

 speck for example, a Protamceba or a Protogenes has attained a certain size by 

 the assimilation of foreign albuminous matter, it falls into two pieces; there is 

 formed a constriction around the middle, which finally leads to the separation of 

 the two halves. Each half becomes rounded, and then appears as an independent 

 individual, which commences anew the simple play of the vital phenomena of nu- 

 trition and propagation. In other Monera (VampyreHa) the body, in the process 

 of propagation, instead of two, falls into four equal parts; and in others again 

 (Protomonas, Protomyxa, Myxastrum), at once into a large number of small globules 

 of slime, each of which again, by simple growth, becomes like the parent body." 



The marine Rhizopoda are usually furnished with a horny shell, and live, singly 

 or socially, in shells having a series of chambers. The Sub-class Monothalamia 



