VIL] ANIMALS AND PLANTS. 167 



The apparent suddenness of the appearance of multi- 

 tudes of such organisms as these, in any nutritive fluid 

 to which one obtains access, is thus easily explained. 



During these processes of multiplication by fission, 

 the Heteromita remains active ; but sometimes another 

 mode of fission occurs. The body becomes rounded 

 and quiescent, or nearly so ; and, while in this resting 

 state, divides into two portions, each of which is 

 rapidly converted into an active Heteromita. 



A still more remarkable phenomenon is that kind 

 of multiplication which is preceded by the union of 

 two monads, by a process which is termed conjuga- 

 tion. Two active Heteromitce become applied to one 

 another, and then slowly and gradually coalesce into 

 one body. The two nuclei run into one ; and the 

 mass resulting from the conjugation of the two 

 Heteromitce, thus fused together, has a triangular 

 form. The two pairs of cilia are to be seen, for some 

 time, at two of the angles, which answer to the small 

 ends of the conjoined monads ; but they ultimately 

 vanish, and the twin organism, in which all visible 

 traces of organisation have disappeared, falls into a 

 state of rest. Sudden wave -like movements of its 

 substance next occur ; and, in a short time, the 

 apices of the triangular mass burst, and give exit to a 

 dense yellowish, glairy fluid, filled with minute gran- 

 ules. This process, which, it will be observed, 

 involves the actual confluence and mixture of the 

 substance of two distinct organisms, is effected in the 

 space of about two hours. 



The authors whom I quote say that they "cannot 



