186 On the Genetics of the Ciliate Protozoa 



at the second division. (See Praiidtl (1906), Enriques (1907), Pop.ift" 

 (1908 a), etc.) 



8. It is possible that a ciMlain ainninil nf (_-vti)])lasiii is always 

 exchanged during conjugation'. This has hccii dcsi-iihcil in at least 

 one form — Stentor. (See Mulsovv, 1913.) In the parasitic t'orni Aiio- 

 •plophrya, according to Collin (1909), each conjugating individual receives 

 half the meganucleus of its partner-. After the exchange, however, it 

 degenerates and di.sappears. The meganucleus is not known to behave 

 in this manner in other forms. 



9. After this brief account of divisicm and conjugation", we may 

 consider the interpretation to be put upon these events and the com- 

 parisons which may be drawn between them and the conditions which 

 obtain in other animals. Failure to make a correct comparison, confusion 

 of ideas, and misuse of words, have unfortunately introduced a great 

 many unnece.s.sary complications into this relatively simple matter. 

 A real analysis of the vital phenomena of the Ciliata is possible onl}' 

 when we discard the erroneous a priori deductions of the modern cell 

 doctrine and certain evolutionary speculations — with all their mis- 

 conceptions and slipshod phraseology — and consider these organisms 

 objectively. I have pointed out elsewhere how this may be done, so 

 that it will be unnecessary to repeat what I have already wi'itten. 

 (See Dobell, 1911.) I shall now merely state a few obvious homologies 

 between a ciliate and a metazoon which are fundamentally important 

 for a comprehension of what follows. These homologies are as correct 

 as I believe it possible to make them with the words at my command. 

 But I would emphasize here that the very peculiar organization and 

 behaviour of the ciliates — which are in many ways radically different 

 from all other organisms — render all descriptions of them, in terms 

 borrowed from those other organisms of a different order, only approxi- 

 mately true. 



10. First, a ciliate is not unicellular — it is not the homologue of 

 one cell in the body of a metazoon, but is homologous with an entire 



' For tliose who regard the chondriosomes, and not the chromosomes, as the "bearers 

 of hereditary characters," it may he of interest to add that chondriosomes have been 

 described in many different ciliates, bnt their behaviour during conjugation has not yet 

 been studied. 



- First described in Anoplophryu by Schneider, in 1886. 



'■' It should be stated that the conjugation here described is that characteristic of most 

 free-living ciliates. In some parasitic forms quite different processes occur. I may 

 mention Oixdina, which forms small ciliated gametes (Neresheimer, 1907; Metcalf, 1909), 

 and IcIUIiyuphthirius, which exhibits a peculiar form of self-fertilization (Neresheimer, 

 1908; Buschkiel, 1911). 



