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LECTURES ON BIOLOGY 



single plates firmly together, thus giving to the whole the neces- 

 sary solidity. For some time the two animalcules remain in 

 the position of shell-opening pressed against shell-opening, con- 

 nected only by a bridge of protoplasm, but suddenly the connect- 

 ing cord breaks, the two animalcules crawl apart, and the 

 division is complete. Very soon afterwards the living contents 

 of the two shells have by growth regained the normal size. 



FIG. 53. A MICRO-AQUARIUM. FORAMINIFERA AND CILIATES (MAGNIFIED). 



On the left, below, on the branches of an Alga, a Foraminiferon (Euglyplia 

 alveolata) ; crawling on the bottom a shell-animalcule (Stylonycliia mytilus) ; 

 above, swimming, two slipper-animalcules (Paramcecium caudattim) ; a third 

 attacked by a ciliate infusorian (Didinium nasutum}. Below, hanging from the 

 branch of an Alga, three bell-animalcules (Vorticella nebulifera) ; on the stone, a 

 trumpet-animalcule (Stentor roeselii). 



Among all protozoans the Ciliates occupy undoubtedly the 

 highest position. Indeed it seems no exaggeration to say that 

 there is as great a distance between an Amoaba and a Ciliate, as 

 between the sponge or polyp and a mammal. We are continually 

 filled with wonder when we observe the differentiations of which 

 a simple cell is capable. In the Ciliate we find as perfect a 



