668 



THE AMEBIC AX NATURALIST [Vol. XLIX 



for computing the volume of a prolate spheroid (V = 

 1/Qirld 2 ) the difference is 771 cubic m. in favor of the 

 former, although relatively this approximates only 3 per 

 cent. 



A question of some interest is at once suggested, 

 namely, the possibilities for nourishment and develop- 

 ment in cells of large and of small volume, inasmuch as 

 one with a maximum volume has relatively less surface 

 through which nourishment may be obtained. Thus 

 growth may be retarded. 



III. Discussion of Results 

 The close bred forms on the basis of the characters 

 studied in the given population have been found more 

 variable as to both length and diameter, more highly 

 correlated, and larger taking into consideration length 

 and volume. The value of the conclusions in their ap- 

 plication to the solution of problems of evolution is de- 

 pendent on the logical application of cause and result as 

 well as the methods of the investigation. 



That the two groups of zygospores are comparatively 

 close bred and cross bred will scarcely be denied, par- 

 ticularly when it is remembered that in lateral conjuga- 

 tion nearly all adjacent pairs of cells in a filament had 

 united in the process, each pair producing a zygospore, 

 all pairs having originated from the same cell. With 

 the material taken from a part of a mass a few cen- 

 timeters square, a sample of a whole population has been 

 utilized, and from what is known of the reproduction of 

 Spirogyra, it may be assumed with reasonable certainty 

 that the entire mass had its origin from zygospores pro- 

 duced in a few filaments the preceding year. With prac- 

 tically all zygospores measured in each filament, the 

 criticism that isolated zygospores of mixed descent were 

 studied, and that greater variability would be expected in 

 those produced by lateral conjugation, loses its force. 

 Furthermore it is believed that all investigations thus far 



