F. BATES ON SEXUALITY IN THE ZYGNEMACE.E. 105 



several years. To prove this he concludes his article by saying, u If 

 the mode of 'lateral' conjugation described by De Bary, Wood, 

 and others as taking place between adjacent cells of the same 

 filament in Zygnema and Spirogyra be founded on correct observa- 

 tion, all idea of sexuality of the filaments must be abandoned in 

 these cases." Now, to my mind, and according to my experience, 

 this concluding remark effectually disposes both of Mr. Bennett's 

 conclusions, and his experiences extending over several years, for I 

 will venture to affirm that if anyone will seriously commence the 

 collecting of these plants on the 2nd day of April, he will be the 

 most unfortunate of Spirogyra hunters if he does not meet with at 

 least two species, in which lateial conjugation is going on abun- 

 dantly, before the ensuing May-day. By the light of my own 

 experience I will now examine Mr. Bennett's points seriatim. 

 Firstly, as to differences in the sizes of the cells. If anyone will 

 take up a descriptive work on the Zygnemaceo?, he will find such 

 entries as : — Sp. cells "05 to "065 mm. by 2^ to 10 times longer ; 

 sp. *032 to *05 mm. by 2 to 4 times longer ; sp. -024 to "03 mm. 

 by 3 to 8 times longer ; '012 to '015 mm. by 8 to 16 times longer. 

 And in Mesocarpus sp. "012 to *018 mm. by 5 to 10 times longer ; 

 sp. -007 to -015 mm. by 7 to 12 times longer; and so on. Here 

 is variation enough in all conscience 1 Moreover, it has to be 

 admitted that conjugation must have commenced before even a guess 

 can be made as to which is a male and which a female thread or 

 cell. Now, when we consider the many curious changes which take 

 place in the form, &c, of cells at the time of conjugation, we must 

 needs be careful how we draw conclusions from them on which to 

 base a theory of sexuality. Again, one may find mixed in the 

 same gathering, of one and the same species, threads having the 

 spore cells cylindrical and longer than the spores, or swollen and 

 more or less wider than the spores ; or so abbreviated that the 

 spores are crowded together and placed sideways, being longer 

 than their cells ; these are of very common occurrence in Spirogyra 

 longata, porticalis, and condensata. Considering all these things, 

 then, how can we place any value or reliance on conclusions based 

 on an infinitesimal increase in the diameter of one cell over 

 another ? I may further state that I have carefully examined the 

 conjugated cells of Spirogyra porticalis (the species chiefly operated 

 upon by Mr. Bennett) and, where the cells have preserved their 

 cylindrical form, I have not found any appreciable difference of 



