104 



On Sexuality in the Zygnemace2E. 

 By F. Bates. 



(Read, November 28th, 1884.) 



Mr. A. W. Bennett, in an article recently contributed to the 

 Linnasan Society,* seeks to maintain that there are well-marked 

 and certain characters whereby the sexual nature of the filaments 

 in the Zygnemacece may be determined. The chief points on which 

 he relies to prove his case are — 1. The difference in size of the 

 cell; in the Zygnemece, the so-considered germ cells being the 

 largest ; whilst in the Mesocarpece the contrary is the case. 2. 

 That the portion of the conjugating canal contributed by the germ 

 cell is shorter and wider than that contributed by the sperm cell. 

 3. That the protoplasmic contents of the cells always travel in one 

 direction : — that is, that in scalariform conjugation the contents 

 of the cells of one thread invariably pass over into the cells of the 

 other thread with which it is conjugating ; and 4. That in 

 Mesocarpus the spore, which is formed in the conjugating canal, 

 never occupies its centre, except in such cases where the spore is 

 large enough to occupy the whole of that space. He also regards 

 this production of the spore in the conjugating canal as exhibiting 

 a more rudimentary differentiation of the sexual elements. 



Many distinguished cryptogamists have, before Mr. Bennett, de- 

 voted much attention to this question of the sexuality of the threads 

 in these Algas (when such obvious facts as difference in the size of 

 the cells, position of the spores, &c, must have come under their 

 notice, but were doubtless set aside as being inconstant and there- 

 fore unreliable), and although none have positively asserted that 

 sexuality may not exist, with scarcely an exception it has been 

 concluded that no safe, constant, and reliable, sexual characters, 

 which will enable one to say which is a male and which is a female 

 thread, or cell, are discernible. 



Mr. Bennett states that his observations have extended over 



* On " Keproduction of the Zygnemacese : a contribution towards the 

 solution of the question, 'Is it of a sexual character ?'" "Journal of the 

 Linnjean Society," April, 1884, Vol. xx, No. 130, pp. 430-9. 



