F. BATES ON SEXUALITY IN THE ZYGNEAIACE.E. 107 



Bennett has not been able to meet with it during his observations. 

 Lastly, on point 4. as to that form of conjugation in which the 

 Zygospore is formed in the conjugating canal. Mr. Bennett states 

 that the spore never occupies the middle of this canal, except in cases 

 where, from its large size, it fills the whole of that space ; otherwise 

 it is always formed at one side, and at that side nearest the so-con- 

 sidered female cell, which he also states to be constantly shorter than 

 the supposed male cell. I am prepared to admit (and to give him 

 credit for this observation) that the spore is mostly situated at one 

 side of the conjugating canal ; but it is so frequently otherwise — or 

 situated at the centre — as to destroy any value the observation might 

 seem to have, in helping to determine the sexuality of the cells. As 

 to the spore when lateral being always adjacent to a short female 

 cell, this is still less to be depended upon. I find it subject to great 

 variability. It is not easy to ascertain the exact position of the spore, 

 and to accurately measure the mother-cells in these delicate plants ; 

 the conjugated threads being so involved that it is only here and 

 there one can get a view of the two cells, and the spore, accurately 

 in focus at the same time. Out of a number of such that presented 

 themselves in a position to be accurately viewed and measured, I 

 selected seven in which the spore was lateral, and seven in which it 

 was central, and measured all the cells. I found that in the former 

 case the cells were, in a majority of cases, longest in those con- 

 sidered by Mr. Bennett to be males, these varying in length from 

 •091 to -13 mm. ; whilst the so-considered female cells varied in 

 length from *078 to -104 mm. But I also met with so-considered 

 female cells which were longer than their attached male cells in the 

 proportion of from 5 to 6 given spaces to 4, or an average dif- 

 ference of *04 mm., the female cells being longest by those figures. 

 In those cases where the spore was central, I found a great, or even 

 greater, difference in the comparative length of the two attached 

 cells. In one case a cell was exactly double the length of the other 

 cell to which it was yoked. So here again we are met with such 

 an utter want of uniformity as to baffle all attempts to determine 

 the sexuality of the cells. A figure is given by the author of a 

 spore of a Spirogyra germinating in a direction totally opposed to 

 all previous experience. I do not deny that he may have seen a 

 spore germinating after the fashion figured, but it must most cer- 

 tainly be regarded as most exceptional and abnormal. 



Mr. Bennett further has made the remarkable discoverv that the 

 Journ. Q. M. C, Series II., No. 11. k 



