The Conjugation o) Zygogonium ericetorum Kutz 239 
short account, illustrated with two figures, of the conjugation (as 
observed in dried material) of Zygogonium ericetorum, under the 
name of Zygogonium duly mum Rabenh. He considered the latter 
as probably only a form of Zygogonium ericetorum, which is 
undoubtedly the case. West (8, 10), for instance, has examined 
the original specimens of Zygogonium didymum Rabenh ( =Z 
Agardhii Rabenh.) in the herbarium of the British Museum, and 
states that they are identical in every respect with Zygnema 
(Zygogonium) ericetorum (Kutz.) Hansg., a conclusion which, it will 
he seen, is further strengthened by the observations recorded below. 
The process of conjugation described by de Baryfor “ Zygog. 
didymum ” is peculiar and does not quite resemble what has been 
observed in any other member of the Conjugate. He states that 
the conjugating cells (which are in different filaments) put out 
protuberances which meet and adhere at the extremeties, but 
instead of fusion taking place and the two cells put in communica¬ 
tion by means of a “ conjugation-canal,” the greater part of the 
protoplast of each cell passes to the extremity of the protuberance 
and is there cut off from the main body of the cell—in which, 
however, a remnant of protoplasm is left—by a curved partition- 
wall as a special cell or gametangium (3, Plate VIII, Fig. 19, 1 a, b). 
The thick wall separating the two gametes becomes gradually 
absorbed, and the latter fuse to form an elliptic zygospore, which 
surrounds itself with an independeut wall. 
The special cell or gametangium, cut of in the protuberance 
of each conjugating-cell, 2 is exactly comparable to the special 
gametangia observed in Temnogametum and Sirogonium. These 
genera, however, differ from Z. ericetorum in the fact that the 
sterile cells cut off at the same time as the gametangia, each 
"contains a complete protoplast, with chromatophore and nucleus, 
and resembles an ordinary vegetative cell, while the corresponding 
sterile cells of Z. ericetorum, with their slight colourless proto¬ 
plasmic contents, are much better compared with the relics of 
the gametangia of Mougeotia or Pyxispora —in which genera, 
likewise, the whole of the protoplast of the conjugating cell is 
' Reproduced in various works, such as Oltmanns, Morph, d. Aigen, 
Vol. 1, Fig. 41, 6, on p. 66; also Cooke, British Freshwater Algae, Vol. 2, 
Plate 40, Fig. 3, c. 
* The term “ progametangia,” applied to these conjugating-cells by 
Wille (13), seems unnecessary; but it should be noted that the word has 
been applied—quite incorrectly—by several authors to the actual gametangia 
cut off in the conjugation-tubes. 
