MAUPAS'S RESEARCHES ON OILIATE INFUSORIANS. 607 



the other a micro-nucleus ; and on fission each set so formed 

 constitutes the nuclear apparatus of the first ofifspring of the 

 exconjugate. During these processes the original meganuclei 

 of the gametes have undergone disorganisation and ab- 

 sorption. 



We may express the above still more briefly thus : — Two 

 Ciliata of the same species approach by their oral surfaces ; 

 the original micronuclei by repeated bipartition form a pair of 

 pronuclei; one pronucleus in either gamete migrates into the 

 other to fuse with the stationary pronucleus therein; then 

 a new nuclear apparatus is constituted by the bipartitions of 

 the copulation-nucleus ; the gametes now separate to found 

 each a new life-cycle of the species. 



Several important variations occur on the schema given 

 above; thus, in Coleps hirtus, &c., with a single micro- 

 nucleus, stage G is doubled (^ ^), so that we have eight 

 nuclei of the form Z^, instead of four of the form Z^ ; two of 

 these become micronuclei, as in Colpidium; and it seems 

 probable that the other six are transformed into meganuclei, 

 which, by interfusion, have their number reduced to 2. 



As a more complicated variation I may cite Paramoecium 

 caudatum, where the stages are identical with Colpidium 

 as far as E, and stage G is doubled as in Coleps. 



We may represent the process of reconstruction in (a single 

 exconjugate) Paramoecium caudatum by the following 

 equations, using the symbol for multiplication by zero ( x 0) 

 to designate the elimination of certain of the nuclei descended 

 from the conjugation-nucleus : 



(a) Z = 8Z» (Stages F, G, G^. 



ib) 8 Z' = 4M + m + 3 Z^ X (Stage H). 



(c) 4M + m = 4M + 2m' = { 2M + m '} + {2M + m'] (1st fission). 



(d) 2M + mi = 2M + 2m2= {M + m*} + {M + m^ (2nd fission). 



Here one of each of the four pairs of nuclei Z^ becomes a 

 meganucleus, their sister (micro-) nuclei all aborting save one. 

 This divides during the first bipartition, of which the offspring 



