42 West & West . — Observations on the Conjugatae . 
do better than quote Bennett and Murray 1 . £ As De Bary 
has pointed out — and his statement is confirmed by nearly 
all more recent observers — the direction of conjugation is 
clearly governed by some physiological law, the movement 
of the protoplasm between the two filaments almost invariably 
taking place in one direction only, so that one of the two 
conjugating filaments is entirely emptied, while the other is 
filled with zygosperms.’ In this paper we shall refer to the 
filament filled with zygosperms as the female, and the emptied 
one as the male filament. 
As a rule a zygospore is formed by the fusion of the 
contents of two conjugating cells, but very rarely it is seen 
that three cells (two male and one female) have participated 
in its formation 2 (vide Fig. 66) ; in this way even three 
filaments may be concerned in the production of one zygo- 
spore. That this manner of conjugation is abnormal is proved 
by the larger number of failures than of completed attempts 
(vide Figs. 67 and 69). In those species belonging to the 
sub-genus Zygogonium , in which the zygospore is formed in 
the conjugating-tube, conjugation between three cells entails 
the production of two somewhat smaller zygospores, as in the 
example figured (Fig. 63). 
Two filaments are generally concerned in an example of 
scalariform conjugation, but three, four, five, and even six are 
not uncommonly seen 3 . In such cases we have to deal with 
either polygamy or polyandry, and after the examination of 
hundreds of examples, we can confirm Bennett’s statement 
that the former is rather more frequent, the ratio of the 
frequency of polygamy to polyandry being about i-6 : 1. 
During conjugation the filaments frequently assume a darker 
colour, this being most marked in Spirogyra angolensis , in 
which species they become blackish- or brownish-purple. 
1 Bennett and Murray, A Handbook of Cryptogamic Botany, p. 2 66. 
2 Cf. Z. cruciatum in West, Sulla Conj. delle Zygn., 1 . c., t. 13, f. 13; also 
Spirogyra , sp. in Borge, Siber. Chlorophy., Bih. t. Sv. Vet.-Akad. Handl., Bd. 17, 
Afd. 3, No. 2 (1891), t. i, f. 2. 
8 West, 1 . c., t. 12, f. 1. 
