6^2 



THE AMERICAN NATURALIST [Vol. XLIX 



method of nature, in which to bring about a change evi- 

 dent to mankind. That the weight of evidence, so far as 

 investigations have gone, is against evolution by means 

 of the other variations noted, makes the explanation the 

 more plausible. While it is true that Bateson ( '14) has 

 urged the consideration of the proposition that organic 

 changes occur through the loss of inhibiting factors — de- 

 factorations — such a double negative theory assumes a 

 decreasing complexity instead of an increasing com- 

 plexity of protoplasm, as already pointed out by Castle, 

 ('15) and seems impossible to maintain. 



On the interpretation here presented, the diversity of 

 organic forms is more complex than earlier imagined, 

 and the problem of positive racial improvement is still 

 far from solution. Loss as well as segregation factors 

 may add new forms which really contain nothing new. 

 To build up and not to break down is the desideratum, 

 and the data obtained would seem to suggest that pure 

 line breeding with the employment of statistical methods 

 to show any progress would be the path leading most di- 

 rectly to the goal. 



VI. Conclusions 



1. Direct Conclusions 



The following conclusions drawn from the investiga- 

 tion are primarily statements of fact, 



1. Zygospores of Spirogyra inflata (Vauch.) produced 

 by lateral conjugation or close breeding (quasi-partheno- 

 genesis) are relatively 26 per cent, more variable in 

 length and 31 per cent, more variable in diameter as 

 measured by the coefficient of variation, than those pro- 

 duced by scalariform conjugation or cross breeding 

 (sexual reproduction). 



2. The size (volume) is greater in the average (mean) 

 zygospore close bred by lateral conjugation, where the 

 mean length is 62.38 j*. + .178, than in the average zygo- 



