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William J. Hod get is . 
not used up in the formation of the gamete. The affinity of the 
alga, however, is further discussed below. 
Since the publication of de Bary’s work (1858) the conjugation 
of Z. ericetorum appears to have been recorded oidy once, and then 
under another name. W. & G. S. West (11) in 1894 described a 
species of Zygnema under the name of Z. pachydermuni, conjuga¬ 
ting specimens of which were obtained “ from the surface of mud 
in a warm stream in the crater of Grande Soufriere in the West 
Indian island of Dominica.” The process of conjugation was 
described as taking place exactly as in those species of Zygnema 
in which the zygospore is lodged in the conjugation-canal (and 
which were therefore placed by Kiitzing, in 1843, in the “genus” 
Zygogonium '), and no special gametangia were observed to be cut 
off prior to fusion of the gametes. 
Later, West and Starkey (9, 10) very thoroughly re-examined 
the original material of Zygnema pachydermuni and found that 
“ vegetatively this alga is identical with Z. ericetorum ; ” and thus 
concluded that “ Z. pachydermuni ” was a conjugating specimen of 
the common species. This, if correct, meant that Z. erictorum, 
under the conditions in which it was found in the W. Indies, 
conjugates in exactly the same way as such a species of Zygnema as 
Z. Ralfsii. Further, they considered that since the process of 
conjugation described by de Bary had not been confirmed by 
anyone since 1858, that his account of “ Zygogonium didymum ” 
may have been based on an abnormality ; and that it could not be 
used as a basis for the genus Zygogonium , as proposed by de Bary. 
It appears that these conclusions, although reasonable at the 
time in view of our meagre knowledge of the conjugation of 
Z. ericetorum, must now be modified, since the present writer has 
been fortunate in finding the typical terrestrial form of Z. ericetorum 
in conjugation, and, as will be seen below, has been able to confirm 
de Bary’s account (described under “ Zygogonium didymum ”) as 
far as it went, while a few details have been added. It now seems 
impossible to doubt that Zygogonium ericetorum must be kept in a 
genus apart from Zygnema. 
' For reasons why Kiitzing’s Zygogonium cannot be upheld see (8) and (10). 
De Bary (3) proposed putting the genus Zygogonium on a new basis, namely, 
that of the peculiar processof conjugation observed in “ Zygogonium didymum" 
( —Z. ericetorum). If this is accepted, then Zygogonium contains only one 
species (Z. ericetorum). The subject is further discussed below. 
