MATJPAS'S RESEAEOHES ON CILIATE INFUSORIANS. 609 



place, in which the meganuclei are distributed between the 

 offsprings while the micronucleus undergoes bipartition : the 

 normal state of the species is reached in one offspring of the 

 second, and in six of the third fission. 



The processes of nuclear reconstitution in Vorticellines, with 

 the fissions necessary to bring back the type form, possessing 

 a single mega- and micro-nucleus, are represented in the 

 following equations. In each case a vinculum is put 



above the normal form. 



8Z»=7M-hm (Stage H). 



7M + m = 7M + 2mi= {3M + m'}-|-{4M + mi} (1st Bssion). 

 3M + mi = 3M + 2m2 = {M + m2} + {2M + m2} (2nd fission). 

 4M + mi = 4M + 2m»= {2M + m2} + {2M + m2} „ 

 2M + m2= 2M + 2m3= {M + m^} + {M + m^} (3rd fission). 



The relations are further complicated by the reduplication 

 of the micronucleus of the microgamete in the beginning of 

 stage A ; both these micronuclei undergo the bipartitions of 

 stages B and C ; but only one of the eight nuclei (2v^) so 

 formed divides in stage D, which is thus identical with that 

 of the megagamete. A similar reduplication of the micronu- 

 cleus occurs in both the isogamous gametes ofEuplotes. 



The fusion of the two cytoplasms takes place at the end of 

 stage E. The old meganucleus undergoes fragmentation, and 

 its pieces may be all absorbed, or some may finally fuse with 

 the new meganuclei. 



I have cited a number of distinct cases from Maupas to 

 show that, with wide differences of detail, the phenomena are 

 everywhere essentially the same in the Holotricha, Hetero- 

 tricha, Hypotricha, and Peritricha : his observations on the 

 Suctoria or Acinetina show that the law may be extended to 

 this group — a sure proof, if one were needed, of its true 

 affinities. 



A series of elaborate discussions follows the systematic review 

 of the phenomena of conjugation in the Ciliata. The double 

 nature of the nuclear apparatus in this group is explained by a 



VOL. XXXII, PART IV. NEW SER. S S 



