182 ANIMALS AND PLANTS vi 



During these processes of multiplication by 

 fission, the Hdcromit<i remains active ; but some- 

 times 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 Hetcromita. 



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 

 conjugation. Two active Heteroniitco become applied 

 to one another, and then slowly and gradually coa- 

 lesce into one body. The two nuclei run into one ; 

 and the mass resulting from the conjugation of the 

 two Heteromitcc, thus fused together, has a tri- 

 angular 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 organ- 

 ism, 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 

 granules. 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 



