178 On the Genetics of the Ciliafe Protozoa 



because the effects of conjugation with uurehited individuals have never 

 been studied simultaneously. 



120. This seems the proper place at which to mention the i)heno- 

 nienon of "reconjugation" discovered by Enriques (1908). He found 

 that exconjugants of Chilodon, instead of dividing, sometimes proceed 

 to conjugate again — either with other exconjugants or with ordinary 

 conjugants. The same thing has been recently observed in Paramecium 

 by Klitzke (1914). Conjugation may be effected by an exconjugant or 

 by the products of its first fission. These observations clearly show 

 that the stimulus to conjugation — whatever it may be — may exist 

 without a series of asexual fissions having intervened since a preceding 

 conjugation. The fate of the progeny of " ex-reconjugants" has not 

 been adequately described. 



121. I may here mention some cases of what may be called "mis- 

 conjugation." Doflein (1S)()7) says that if conjugating Parainecia are 

 forcibly separated, they will reunite with other individuals — either 

 non-conjugants or conjugants of a different staged Abnormal con- 

 jugations may thus be brought about, the results of which are not 

 recorded. Many observers have reported abnormal conjugations of 

 three or more individuals-. Several such unions of three individuals 

 were observed by Mulsow (1913) in Stentor: but to my knowledge no 

 investigator has yet ascertained the consequences of these misconjuga- 

 tions. Doflein (1907) further describes, in Paramecium piitrinum and 

 Styloiiychia mytilus, "agamic fusions" of two individuals, "cytoplasm 

 with cytoplasm, nuclei with nuclei, so that an apparently quite normal, 

 but relatively very large individual resulted." The subsequent be- 

 haviour is not described'. 



122. In conclusion, a word may be said about "hybridization" in 

 ciliates — I mean cross-conjugation between two individuals of different 

 specie-s. I know of but a single case in which this is alleged to have 

 happened. Apart from this, there appears to be no recorded case of 

 "crossing" even between individuals belonging to different pure lines 



' Doflein gives an illustration of this, which, according to Klitzke (1914), really depicts 

 a conjugation between an ordinary eonjugaut and a "reconjugant" (§ 120). This inter- 

 pretation certainly appears plausible. 



- These are described, for instance, by Stein, Eugelmann, Jickeli, Gruber, Plate and 

 Maupas — among the older observers — and generally in Stylonychia or P. putrinum. 



' But Engelmann said that these compound organisms {Stylonychia) can grow and 

 multiply — a statement as yet unconfirmed. Maupas believed that such fusions have 

 nothing to do with conjugation — the fused animals being monstrous, and their divisions 

 irregular and incomplete. 



