26 



INFUSORIA. 



which misled Ehrenberg to suppose that these tiny 

 organisms were possessed of numerous stomachs — 

 hence they were formerly named Polygastria,* or 

 many-stomached animalcules. 



Fig. 13 — FIGURE OF S'WAX-NECK AXD ITS DH'ISIOXS. 



By no means the least remarkable part of the 

 history of the Infusoria is their mode of propagation. 

 This is usually accomplished by the spontaneous 

 division of the adult animalcule into two or more 

 portions, each of which in a short time becomes in 

 every respect a complete individual. We remember 

 in our boyish days hearing of some strange machine 

 for grinding old people young again, and smiled at 

 the idea, little thinking that the conversion of old 

 animals into young ones was, in sober truth, one of 

 the commonest operations of nature. The body of 

 an animalcule about to propagate in this manner, 

 becomes at first slightly elongated, and a line, more 

 transparent than the rest, is seen to cross its middle 

 portion ; a constriction next becomes apparent at 

 each extremity of tlie line indicated, which, becoming 

 more decided and growing gradually deeper, at 

 length divides the animalcule into two halves, only 

 connected with each other by a narrow isthmus, and 

 as this grows tliinner and thinner, a slight effort on 

 the part of either of the now nearly distinct portions 

 is sufficient to sever the frail bond of union and 

 complete the separation. In some elongated species 



* TToXvs, polus, many; yaa-Tep, yacnphs, gaster, gastros, tlie sto- 

 mach. 



