RHIZOPODA AMCEBfNA. 77 



It would be difficult to say exactly what is the form these creatures 

 assume. They frequently have the appearance of small, rounded 

 masses, like drops of water ; but, whatever their form may be, it is 

 often so unstable, that it changes, so to speak, every moment. 

 This instability is one characteristic manifestation of life in the 

 A?nceb<e, which are naked beings, without any apparent organisation ; 

 in fact, they may be said to occupy the first step in the scale of 

 creation. 



If we examine one, at first it looks like a transparent immovable 

 drop. We then see it putting forth a pseudopod, which, gliding like 

 a streak of oil under the thin covering glass, as we view it through a 

 microscope, begins by fixing itself to some point, afterwards slowly 

 attracting to itself the whole of its body mass, and thus gradually 

 increasing its bulk under the observer's eye. 



The AmoebtE, according to their dimensions and degree of develop- 

 ment and activity, successively emit a greater or smaller number of 

 pseudopod s, none of which are precisely alike, but after having 

 appeared for a short time, each successively will be seen to re-enter 

 the common mass, with which it becomes completely incorporated. 

 Variable in their respective forms, these pseudopods present ap- 

 pearances quite different in the several genera. They are more or 

 less attenuated, and often branching ; sometimes they spring in all 

 directions from the animal mass. 



If we ask how these animals are nourished in which no digestive 

 apparatus can be distinguished, the question is difficult to answer. 

 It was once thought that they are nourished by simple absorption, 

 and by absorption only. In the interior of the gelatinous mass which 

 constitutes these animals, however, microscopic algae are frequently 

 discovered. Indeed, some of them are very voracious feeders, and 

 may be seen completely stuffed with diatoms, or pretty green desmids. 

 " We can conceive," says Dujardin, " how these objects have pene- 

 trated to the interior, if we remark that in creeping on the surface of 

 the glass, to which they adhere very exactly, the Amoeba, can be 

 made to receive by pressure foreign substances into their own bodies 

 by means of the alternate contraction and extension of the various 

 parts natural to them. 



The Amaboe are often observed to be tinted red or green ; this 

 apparently arises from a special colouring matter which has been 

 absorbed into their body substance, and the brightness of their colour 

 is in direct proportion to their state of health. 



The question arises, How do these creatures, so simple in then 

 organisation, propagate their species ? 



