No. 587] VARIABILITY AND AMPHIMIXIS 655 



explained on the basis of the segregation of size and shape 

 characters. Similar results were obtained by East ('11) 

 for maize and Hayes ('12) for tobacco. 



Jennings ('11) extending and summarizing his breed- 

 ing experiments on Paramecium concluded that 



The progeny of conjugants are more variable, in size and in certain 

 other respects, than the progeny of the equivalent non-conjugants. 



Later ('13) continuing his investigations he stated that 

 conjugation increased the variability in the rate of repro- 

 duction. In a subsequent part of the present paper a 

 somewhat critical review of the data and conclusions 

 therein noted is presented. 



3. Material 



In obtaining material early one April for the labora- 

 tory work of a class in biology, the collection being made 

 in a small pool resulting from the overflow of a rivulet, a 

 peculiar species of Spirogyra was noticed in which both 

 lateral and scalariform conjugation was taking place often 

 in the same filament. It was at once suggestive that a 

 comparison of the variability in the two groups of zygo- 

 spores would present facts of interest in connection with 

 the effect of close breeding and cross breeding on varia- 

 bility as well as affording evidence as to the theories of 

 amphimixis. 



The species was first determined as Spirogyra quadrata 

 (Hass.) but subsequent examination indicated that it 

 should be classified as Spirogyra inflata (Vauch.). 



The material utilized for the measurements was all pro- 

 cured at one time from a restricted area one or two inches 

 square on the surface of the pool and included only the 

 one form of Spirogyra, that alone being present as a mass 

 3 or 4 inches in diameter. Inasmuch as both lateral and 

 scalariform conjugation occasionally took place in the 

 same filament (Fig. 2) a suggestion that two species were 



