C. DOBELL 175 



seems to me to lie in the fact that they afford additional grounds for 

 doubting the validity of Jennings's conclusions concerning " biparental 

 inheritance "(§ 110). It maybe noted further that some evidence is 

 given that the differences between the surviving lines derived from the 

 same exconjugant tend to disappear in the course of time — a tendency 

 which is of interest in view of what has previously been remarked (§ 109). 



112. It is noteworthy that Pearl's (1907) biometric study of 

 Paramecium led him to a conclusion diametrically opposed to that 

 of Jennings (§ 106). He says: "There is no evidence that conjugation 

 tends to produce increased variability in exconjugants. All the evidence 

 indicates, on the contrary, that conjugation serves... to preserve relative 

 stability of type." The same standpoint is taken up by Enriques (1907), 

 though chiefly on a priori grounds. 



113. A curious observation bearing on the effect of conjugation 

 has been made by Jollos (1913). He states that his arsenic-resistant 

 race of P. caudatum (§ 71) has lost its resistance as a result of conjuga- 

 tion\ Progeny of exconjugants displayed merely ordinary resistance, 

 whereas progeny of non-conjugants (a pai-allel line) continued to display 

 their acquired increased resistance for a long period. If this observation 

 is substantiated and confirmed, it appears to indicate that conjugation 

 is a barrier to the transmission of an acquired physiological character — 

 that it eliminates rather than originates variation. 



114. It was believed by Calkins (1902) and Cull (1907) that the 

 effects of conjugation are not the same on the two members of a pair 

 of exconjugants — the progeny of one tending to survive, of the other 

 to die out. This was interpreted as evidence of " incipient fertilization " 

 in Paramecium — the form studied. When the nature of a conjugant 

 is properly understood, however, it is clear that this is based on a con- 

 fusion of ideas. The conjugant is neither a male nor a female, nor 

 a gamete of any category (§12 et seq.). To speak of " incipient fertiliza- 

 tion " or " incipient sexuality- " in this connexion is meaningless. It is 

 of interest, however, to know whether there is really a difference in the 

 fate of the progenies of a pair of conjugants, and the matter has been 

 exhaustively studied by Jennings and Lashley (1913). They conclude 

 that "if one member of a pair survives, the other member tends to 

 survive also ; if one dies out the other tends to die out also." The 



' After conjugation the resistance is said to disappear "mit einem Schlage": but it is 

 also stated that the progeny of the exconjugants were not tested until two weeks after 

 conjugation, so that the "suddenness" of the loss is hardly demonstrated. 



- Jennings and Lashley (1913). 



12—2 



