126 



THE MICROSCOPE 



Fig. 113.— 



Amoeba. 



dition. These steps have not been obliterated, and amongst 

 the denizens of our ponds and ditches are to be found specimens 

 of many of these early phases of life — specimens so nearly alike 

 that it is quite possible to follow the lines along which one form 



has developed into another. Such a concep- 

 tion leads one to examine the ponds and 

 ditches with a connected idea. 



The class of creatures which represents this 

 least complex form of existence is called 

 Protozoa, quite as simple a name as kangaroo 

 when you become accustomed to it, and to 

 those who remember their classics a much more 

 descriptive one. 

 In almost any pond with weed, a careful search will produce 

 a creature called an Amoeba, which is the least elaborate piece 

 of living animal matter known. One calls it a piece of living 

 matter, for it is nothing more than a morsel of jelly, which changes 

 its shape every minute. This jelly has no case or skin, but, as 

 it does not dissolve, it remains separate from the water like a 

 bubble of oil. It can move its contents to one end of itself, 

 thus increasing for the time being that end and diminishing the 

 other, and so it flows about in any direction, altering its shape 

 to an indefinite extent, forming itself either into a long projection 

 as a tiny trickling stream, swelling out into circular knobs, or 

 doing both at the same time. In this way it slowly moves about 

 without, so far as can be seen, any fixed intention ; and, as the jelly 

 of which it is made is filled with fine particles, the flowing of the 

 fluid creature can be easily watched. Besides these tiny particles 

 there are much larger things rolling about within its substance. 

 These are often recognisable as shells of diatoms and of other 

 tiny creatures that are to be met with alive swimming about 

 in the neighbourhood of the Amoeba. If the Amoeba be care- 

 fully watched, it will be seen that when it comes across something 

 which appears suitable it begins to pour itself out in three or 

 four streams all around the desired object, 

 and these streams, as they meet round the 

 victim, join together. The object thus 

 caught and enclosed remains in the jelly, 

 where it is slowlv dissolved. 



The Amoeba feeds by literally putting 

 itself outside its food. When the victim 

 has been dissolved, the hard and insoluble 

 parts are allowed to escape back into the 

 water, and the portion that is assimi- 

 lated goes to increase the size of the jelly. It is not, how- 

 ever, correct to say that this creature consists of nothing but 

 the granular jelly filled with the remains of the things it has 

 absorbed. It has two primitive organs — one, a small spot of 



Fig. 114.— Villous 

 Amceba. 



