1 76 On the Genetics of the Ciliate Protozoa 



effects of conjugation tend to be the same — not different — for both 

 members of a pair. This deimmstration furnishes the chief evidence 

 for " biparental inheritance" in I'amineciuiii^ (§107). 



115. Enriques (1908) states that in CliUodim, the two conjugants 

 are alike at the beginning of conjugation: but during conjugation they 

 become differentiated into a longer and a shorter. This phenomenon 

 is called "hemisex" — Enriques regarding the longer conjugant' as "half 

 female," the shorter as "half male." What the significance of this 

 "se.Kual differentiation as an effect of conjugation" may be, is obscure. 

 It is quite certain, however, that the phenomenon has nothing to do 

 with sexual differentiation properly so called. For from the point of view 

 of sex, the conjugants are identical — both being hermaphrodite (§ 14). 

 It may be noted that Jcimings (1911 «) has observed a tendency to 

 " equalization " during conjugation in Paramecium. The two members 

 of a pair of conjugants tend to become more alike — not less alike — 

 during the process. 



116. We have seen (| 20) that Maupas regarded "inbreeding" or 

 " interconjugation^" as productive of harmful consequences. Some 

 observations bearing upon this matter have since been made, though 

 they are recorded for the most part incidentally. Cases of apparently 

 successful conjugation between closely related individuals are recorded 

 by Joukowsky (1898), Calkins (190'2), Jennings (1913)-' and others. 

 In other cases, however, such conjugations ajjpear to have been harmful. 

 Baitsell (1912), for example, found that the descendants of a Stylonychia 

 interconjugated readily: but all the exconjugants dietl. Calkins (1912) 

 made similar observations on closely related individuals of Blepharisma : 

 "conjugation is equivalent to a death warrant." Nevertheless, if inter- 

 conjugation really has harmful effects, it is impossible to reconcile this 

 with the facts (1) that conjugation occurs normally between individuals 

 belonging to the same pure line — not between those of different lines 



' It is important to notice what the characters are which are "biparentally inherited" 

 — namely death, or survival. The characters are not racial characters — save in so far as 

 " survival " is a character of every living race. 



- Enriques incorrectly — and inconsistently — calls the conjugants "gametes." When 

 he speaks of an organism as being "half male," I do not understand what he considers 

 the other half to be. The term " hemisex " seems to me ambiguous — or else incorrect. 



' I use this term to denote conjugation between closely related organisms — i.e. between 

 descendants of the same ancestor. The term "inbreeding" is equivocal, and " intercon- 

 jugatiou " seems to me a more suitable word. Conjugation is not an act of reproduction 

 (§ 1.5), and therefore there is really no breeding in the process. 



* In Paramecium putrinum, P. caudatum, and P. aurelia respectively. 



