247 



Fig. 1. 



ought always to suspect that there is something in them requiring 

 close attention. 



Apparently meaningless processes having, as O. Hertwig observes, 

 a striking similarity to the formation of the polar bodies during 

 oogenesis, are seen in the changes 

 (&, c) which take place in the micro- 

 nucleus prior to the actual act of con- 

 jugation. 



Now, the only reproductive pro- 

 ducts with which we are acquain- 

 ted are gametes, including eggs and 

 sperms, and spores. At the stage c 

 there are a number of nuclei formed, 

 resulting from the two mitotic divi- 

 sions B und C. In this particular 

 species, Colpidium colpoda, three 

 of the four (c) in each of the con- 

 jugating individuals are abortive. Do 

 these cell nuclei represent gametes? 

 The answer to this appears to be in 

 the negative; they do not conjugate, 

 happens, each of the functional ones again divides, and the products 

 are those which furnish the actual materials for the conjugation, i. e. 

 the gametes. (In this latter division (D) we have really a virtual fis- 

 sion of sporozooids to form like conjugating gametes.) 



The pole nuclei must therefore be spores, and the process, i. e. 

 the two divisions at B and C must be a sporeformation. The proof 

 of this would undoubtedly be the discovery that in these two divi- 

 sions — probably in the second one — a reduction of the number 

 of chromosomes was accomplished. 



The evidence that this happens is at present not quite complete. 

 In Paramecium, where, as will be seen, quite similar processes 

 occur (Fig. 2 and 3 B and C), it is certain that prior to conjugation 

 a reduction does occur, R. Hertwig^) states that the stationary and 

 the wandering nuclei, i. e. the like gametes {d) ^ possess each 4—6 

 chromosomes, and he describes the normal number of chromosomes 

 in the micronucleus of P. aurelia as 10 2). 



Before an actual conjugation 



1) loc. cit. p. 182. 



2) loc. cit. p. 184. 



