IQI7] 



CUNNINGHAM— SEXUALITY OF SPIROGYRA 



487 



principally upon the fact of lateral conjugation. Occasionally a 

 case of cross-conjugation is presented as evidence, but these cases 

 have been so isolated that they have been of little value. A clear 

 case, then, of cross-conjugation occurring normally in a species 

 would certainly strengthen the position of the advocates of the 

 bisexuality of the filament. 



Vaucher (28), who was apparently the first to work upon 

 Spirogyra, at least upon the problem of its reproduction, figures it 

 in most cases in cross-conjugation. Figs. 1-4 of pi. XXIII are photo- 

 graphic copies from his plates. In his general description of the 

 Conjuguee he says " ordinarily one of the filaments gives while the 

 other receives throughout its entire length. Still it is not rare for 

 the same filament to give in one part of its length and receive in 

 another in such a manner that some of the cells of the tube are 



em 



while 



or receives throughout its entire length, still it frequently happens, 



some 



nately." In regard to Conjuguee condensee, he says "the berries 

 are indifferently lodged in either tube" (Vaucher 28, p. 69)*. . 2 

 Such statements seem to point clearly to cross-conjugation, but 

 when we remember that Vaucher, probably because he was 

 unacquainted with the phenomenon, did not figure or describe 

 lateral conjugation, and that he was dealing in part with species 



illy reproduce in this manner, we have reason to 



norm 



observing: a combination 



scakriform 



have been mistaken 



for cross-conjugation. Just 



the writer. 



XXIII 



came 



under his observation. At first glance the position of 

 the zygotes in the 2 filaments gives the appearance of cross- 

 conjugation. Upon closer investigation it is found that the con- 

 tents of cell (a) probably passed into (b), (c) and (d) represent 



another 



(/) 



regular scalariform manner with (g) and (A) , (i) and (/) 

 and (k) entirely failed to conjugate. 



2 Free translations. 



