REPRODUCTION OF THE HYPOTRICHOUS INFUSORIA 69 



ten days after separation. Entirely different results were ob- 

 tained from three pairs of 'wild conjiigants' of the same species. 

 Of the six ex-conjugants obtained only one died and the remaining 

 five thrived until the observations were discontinued. Cull ('07) 

 also obtained similar results working with the same species. From 

 40 pairs of conjugants taken from laboratory cultures only 12 ex- 

 conjugants or 15 per cent were alive at the end of the month; while 

 from 93 pairs of 'wild conjugants' 70 per cent of the ex-conjugants 

 were alive at the end of the same period. Both Blitschh ('76) and 

 Calkins ('12), working with Blepharisma, have noted the infer- 

 tility of conjugation. Biitschli did not succeed in getting any of 

 the ex-conjugants to live longer than three days, and Calkins not 

 longer than sixteen daj'^s, 74 per cent dying within five days after 

 separation. 



It has been suggested that the greater fertiUty of 'wild' con- 

 jugants than of those from a laboratory culture may be due 

 either to a lack of vitality of the animals in the cultures, or to the 

 fact that in conjugation, if it is to be fertile, there must needs be a 

 new physico-chemical relation established by the fusion of the nu- 

 clei to furnish the factors necessary for the reorganization of the ani- 

 mals, and that the establishment of this relation is not possible in 

 animals which have been subjected to identical conditions. 



The first view cannot be held as an explanation of the fertility 

 of conjugation in these experiments for in the February epidemic, 

 conjugation made its appearance when the animals were dividing 

 at the highest rate they had ever attained. Investigators are 

 agreed that the rate of fission is an indication of the general vital- 

 ity of the animals. Judged in this way, as well as by their general 

 appearance and actions, they were in a perfect physiological con- 

 dition at the time of the appearance of the first epidemic of conju- 

 gation. In the June epidemic inasmuch as the division rate had 

 been considerably lower, it is probable that the general vitality of 

 the animals was not as high as had been the case previously, but, 

 at the time when either of the epidemics appeared, it certainly 

 could not be said that the individuals of the cultures gave evidence 

 of a low degree of vitality. The evidence presented from both 



