250 
William J. Hodgetts. 
the name of Zygogonium didymum Rabenh.), as far as it goes, lias 
been confirmed, and further details added. 
3. The greater part of the protoplast of each conjugating 
cell passes into the protuberance put out by the latter, and is there 
cut off as a special gametangium by a curved partition wall. 
Later, each gamete secretes a thin, independent cell-wall entirely 
round itself. Thus, prior to fusion, each of the gametes is sur¬ 
rounded by a double investment. 
4. In the early stages of fusion of the gametes, the latter 
show a slight morphological distinction. 
5. The inner walls of the two gametangia become only locally 
absorbed during fusion of the gametes, and unite to form a 
continuous membrane round the zygote; and this membrane 
persists as the outermost layer of the wall of the zygospore. 
6. The development of azygospores was observed, and is 
described. 
7. The relation of Zygogonnwi ericetorum to “ Zygnema 
pachydenuum” W.& G. S. West is discussed. 
8. The writer supports the retention of the genus Zygogonium 
on the basis proposed by de Bary (1858), and accepted by Wide 
(1897, 1909), and others. 
1 wish to express my thanks to Professor G. S. West, to whom 
I submitted specimens of the alga, for helpful criticism and advice 
on several points in connection with the paper. 
LITERATURE CITED. 
1. Borge, O. Susswasser Flora Deutschlands, etc, Jena, Heft 9, 1913. 
2. Cooke, M. C., Brit. Freshwater Algae. London, 1882-84, 2 vols. 
3. De Bary, A. Untersuch. iiber die Familie der Conjugaten. Leipzig, 1858. 
4. Fritsch, F. E. The Morph, and Ecol. of an Extreme Terrestrial Form 
of Zygnema (Zygogonium) ericetorum. Ann. Bot. XXX, 
1916. p. 135. 
5. Hassall, A. H. A History of the Brit. Freshwater Algae. London, 
1852, Vol. I. 
6. Palla, E. Ueber cine neue Art und Gattung d. Conjugaten. Ber. 
Deutsch. Bot. Ges. XII, 1894. 
7. Rabenhorst, H. Flora Europ. Alg. Sect. Ill, 1868. 
8. West, G. S. Algae. Vol. 1, Cambridge, 1916. 
