130 



THE MICROSCOPE 



C 



FlQ. 125.- 

 Stentor. 



The Vorticellse are a particularly lovely family resembling 

 groups of dainty lilies. They have a circle of vibrating hairs 

 around the mouth of a bell-shaped body, and are anchored down 

 by a long stalk. If there is a sudden shock and they are alarmed, 

 the stems shut down like corkscrews, and down they go in a 

 flash, taking refuge till the danger is over, and 

 coming out slowly and carefuUy a few moments 

 later. 



A somewhat similar species, the Stentor, has 

 a horn-shaped body, with a powerful ring of 

 hairs around its upper surface. It is a most 

 voracious animal and eats almost anything that 

 is brought to it by the strong current of water 

 which its vibrating hairs set up. One species 

 somewhat like the Stentor has a brown shell in 

 which it Uves. This is fitted with a trap-door 

 attached to the body of the creature in such a 

 manner that when it retreats into its cell or case 

 the shell closes like the nest of a trap-door spider. 

 The Protozoa, therefore, display in their living representa- 

 tives what looks like a fairly complete history of their original 

 development as regards external structure, indicating the creation 

 of a shell or covering, and the creation of ciha and of swim- 

 ming apparatus. It is now interesting to examine the question 

 of their feeding from the same point of view. 



The Amoeba simply pours itself round and engtdfs any object 

 it meets and wishes to feed upon, the object being then gradually 

 dissolved. Some of its constituents mix with the jeEy and 

 are absorbed, and the creature gradually increases in bulk vmtil, 

 being too large for comfort or convenience — ^if such terms can be 

 applied to such a primitive creature — ^it splits itself into two parts, 

 each of which is a perfect animal. 



Those portions of the food which are insoluble 

 are allowed to escape from the jeUy, but there are 

 other portions which, although dissolved, are not 

 suitable or required for nourishment and growth. 

 Water is also taken in with the food particles. It 

 would not do for the Amoeba to be constantly 

 filling itself up with useless material, neither would 

 it be satisfactory for it to be continuously diluting 

 itself. 



Some means must be found to get rid of ,. these 

 waste products, and the means employed are ex- 

 tremely simple. The water and the unnecessary products of 

 the dissolving process form into a bubble, and as soon as such 

 a bubble approaches conveniently near to the surface of the 

 animal, it bursts, discharging its contents into the surrounding 

 water. This is certainly the simplest form of digestion that 



Fig. 126.— 

 Trap - door 

 Animalcule. 



