No. 587] VARIABILITY AND AMPHIMIXIS 683 



spore cross bred by scalariform conjugation, where the 

 mean length is 60.44 ^. + .135, The diameter is approxi- 

 mately the same in both types. 



3. In zygospores produced by lateral conjugation there 

 exists a positive correlation between length and diameter 

 of .1894 = .0460, while in scalariform conjugation the 

 value is .0934 = .0473. This is in general agreement with 

 results obtained by others although here the difference is 

 not significant when the probable error is considered. 



4. In the material studied approximately 45 per cent, 

 of the zygospores were formed by lateral conjugation, the 

 remaining 55 per cent, by scalariform conjugation. 



5. The material studied was strictly homogeneous, and 

 evidently arose from the same parental stock, both types 

 of filaments being intermingled with no structural dif- 

 ferences except those of conjugation. Consequently the 

 differences in variability are not the result of fluctuability. 



2. Indirect Conclusions 

 The conclusions here presented are generalizations 

 based on the present investigation as well as the work of 

 others, and represent propositions concerning which dif- 

 ferences of opinion may exist. 



1. Amphimixis, cross-breeding, etc., decreases and does 

 not augment variability (cumulability) although amphi- 

 mutability may temporarily be increased. 



2. Close bred forms are more highly correlated in re- 

 spect to related characters than cross-bred forms. 



3. Variations, so far as their origin is concerned, may 

 be separated into (A) Normations consisting of (1) 

 fluctuations, (2) amphimutations, and (3) cumulations, 

 and into (B) Abnormations consisting of (1) malsegrega- 

 tions, (2) defactorations, (3) fractionations, and (4) mal- 

 formations. 



4. Cumulations may best be investigated among organ- 

 isms produced asexually, by pure lines, or by close breed- 

 ing than by cross breeding, etc. 



