DjiNDROCOMETi^lS PARADOXUS. 347 



essential process in connection with conjugation is tliat in 

 which the micronuclei are concerned. 



Plate expressed a view that during conjugation there is a 

 recovery of some essential substance of the nucleus from the 

 cytoplasm (see Biitschli, 2) ; but, as Biitschli rightly points 

 out^ it is diflScult to understand upon Avhat grounds Plate's 

 view is based. 



Without going further into a review of the opinions of 

 various writers on conjugation, it may be sufficient to state 

 here the problem which is still in need of solution. Is the 

 interchange of molecules of the cytoplasm of the two con- 

 jugates during conjugation an essential part of the process ? 



This question cannot be answered by direct evidence at 

 present. Whatever interchange of molecules of the cytoplasm 

 there may be during conjugation, no method of observation 

 has yet been discovered by Avhich the course of the molecules 

 of one individual can be traced into the body of the other. 

 It is otherwise with the raicronuclear nucleoplasm, the peculiar 

 structure and staining properties of which enable us to trace 

 with certainty the course of one micronucleus (or germ nucleus) 

 into the body of the other. The direct evidence which we 

 have in the case of the micronuclear fusion is absent in the 

 case of the cytoplasm. It is not reasonable to conclude from 

 this alone that the cytoplasm plays no part in the process of 

 conjugation, nor that conjugation is simply " une affaire de 

 micronucleus." It appears to me that there is some indirect 

 evidence, however, on this point which is worthy of consider- 

 able attention. If the micronuclei alone were concerned in 

 the process, the act of conjugation need be of veiy short 

 duration. In fact, if the germ nuclei were prepared for their 

 transposition a mere momentary contact would be sufficient. 

 It might also be conceived that such a momentary conjugation 

 would be of advantage to the species in lessening the dis- 

 advantageous conditions of the conjugating phase, particularly 

 in the free-swimming Ciliata. In all cases, however, the 

 conjugation is a lengthy process, lasting from twelve to forty- 

 eight hours or more. It is inconceivable that the state of 



