REPRODUCTION OF THE ZYGNEMACER. 431 
My object in the present investigation has been to determine 
whether the difference described by De Bary and Wittrock could 
be substantiated as constant. My observation was first directed 
to the familiar and abundant genera Spirogyra and Zygnema, in 
which the endochrome assumes the form either of spiral bands 
or of two stars in each cell; and the conjugation is of the kind 
known as “ scalariform "—Lthat is, by means of longer or shorter 
canals, connecting the conjugating cells, through which the endo- 
chrome of one cell passes to mingle with that of the other cell. 
Fig. 1. 
Spirogyra porticalis, Vauch. One male filament in conjugation with two 
female filaments. X70. 
In the first place, a strong primá facie argument in favour of 
the sexuality of the filaments exists in the fact that in the enor- 
mous majority of cases, when two filaments conjugate, the proto- 
plasmie contents pass through in one direction only ; that is, 
out of all the cells of one filament (A) into the cells of the other 
filament (B), and not some in one direction, some in the other. 
This is so nearly universally the case, that it cannot be the result 
of chance, but clearly follows some guiding law, and implies in 
itself a differentiation between the two filaments, justifying the 
designation of A as the “male” and of B as the “female " fila- 
ment. The only important statement to the contrary that I 
have met with is by Hassall, who says *:—" It is curious to remark 
that the cells in one part of the same filament will part with their 
contents and remain empty, while in another they will be the re- 
cipients of the contents of the cells of another filament." But in 
33 plates Hassall depicts only two species as conjugating in this 
way; andit is quite possible that the statement may be the result 
ofan error of observation. So transparent are the filamen ts, 
* ‘British Freshwater Algse, vol. i. p. 130. 
