430 MR. A. W. BENNETT ON THE 
Reproduction of the Zygnemaces ; a Contribution towards the 
Solution of the Question, Is it of a Sexual Character ? 
By ArzrzED W. Benwerr, M.A., B.Sc., F.L.S. 
[Read November 15, 1883.] 
THE well-known mode of reproduction which occurs in Spirogyra 
and other genera belonging to the Zygnemaces, known as Conju- 
gation, is always spoken of in botanical text-books as the simplest 
form of sexual union; but I am unable to meet with any record 
of trustworthy observations made with a view to determine 
whether the term is correctly applied; that is, whether there is 
any differentiation between the conjugating “male” and “ female” 
cells. As much as twenty-five years ago that extremely acute 
observer, De Bary, in what is still the best monograph of this 
class of Freshwater Algæ*, stated that he had observed in 
some instances clear differences between the conjugating cells. 
Wittrock, in his “ Freshwater Algæ of Gotland,” + speaks of two 
species in which the “male” and * female" cells are uniformly 
different in size. But most recent writers on the Conjugate 
have either ignored these observations, or at least imply that 
they do not point to any essential physiological differences. 
Thus Wittrocki elsewhere defines a zygospore as “a spore 
formed by an act of fecundation, in which two or more cells of the 
same kind, not sexually different, have participated." Prings- 
heim$ strongly opposes the idea of sexuality in the Conjugate. 
H. C. Wood || says, * Very rarely, if ever, is there any difference 
between the cells before conjugation; and it has not existed in 
any species that has come under my notice." But that writer 
agrees with De Bary (J. c. p. 163) in thinking that “in conjuga- 
tion the first dawnings of sexuality are to be found.” Berkeley, 
by his silence on the subject in his articles on * Conjugation” 
and “ Zygnemacee” in the ‘Micrographic Dictionary, ed. 4 
implies that he does not regard the differentiation as established. 
Finally, Cooke says, “ The cells containing the male and female 
elements cannot at present be distinguished from one another.” 
* ‘Untersuchungen iiber die Conjugaten,’ p. 4. 
t Quart. Journ. Micr. Sci. 1873, p. 131. 
t "*Spore-formation in the Mesocarpez," p. 4, footnote. 
§ ‘Zur Kritik der Untersuchungen über das Algengeschlecht.’ 
|| ‘Freshwater Algs of North America,’ p. 161. 
q ‘British Freshwater Algie, p. 75. 
