Internal Characteristics and Size 109 



to the possibility that part of the disappearing bodily 

 material may be burned up. Again, conjugation in 

 most of the cultures which have been measured was 

 induced by inadequacy of food, and the smaller sizes 

 may be due to cessation of assimilation. Either this 

 factor or some other stops growth, and conjugants may 

 characteristically be immature individuals. Jennings 

 ('11) showed, in fact, that conjugants grew to adult 

 size after conjugation was completed. 1 Pearl ('07) 

 demonstrated that a change of cultural conditions 

 modified the sizes of non-conjugants greatly, but not 

 the sizes of conjugants. This is likely to have been 

 merely because the conjugants were not growing nor 

 undergoing fission; and the food supply was of no 

 effect, once they had been induced to conjugate. 



Variability. All conjugating individuals in a cul- 

 ture were found by Pearl ('07) to be slightly more alike 

 in size than all non-conjugating individuals. This is 

 shown in figure 32, curve B. In four cultures the co- 

 efficients of variation averaged 7.8 for conjugants, and 

 8.3 for non-conjugants. This small difference is easily 

 attributed to the fact that the non-conjugants were 

 of more diverse ages. It was not due to change of 

 form, since the breadths were in proportion to the 

 lengths. Jennings ('11) confirmed these differences 

 of variability, and brought evidence to support the 

 view that the low variability of conjugants was en- 

 tirely due to the uniformity of ages or lack of growth. 

 Remarkable reductions of variability in the body 

 lengths of conjugants as compared with non-conju- 

 gants were demonstrated by Poljansky ('26) in the 

 parasite Dogiella. 



1 More marked growth of ex-conjugate individuals immediately follow- 

 ing conjugation was measured by Dogiel ('25) and Poljansky ('26) in two 

 parasitic genera of ciliates, Cycloposthium and Dogiella. Corresponding 

 reductions in adult size were found to characterize one or more generations 

 just preceding conjugation. 



