REPRODUCTION OF THE ZYGNEMACEX. 439 
the conjugation of four eells which are completely emptied of 
their contents, and is sharply marked off by a cell-wall, it appears 
much more difficult to coneeive of any sexuality in the process. 
I have not, however, been fortunate enough to be able to trace 
the entire course of conjugation in this genus, though I have 
met with the fully formed zygospores intermixed with Mesocarpus. 
lt must be remarked, in conclusion, that if the mode of 
“lateral” conjugation described by De Bary, Wood, and others 
as taking place between adjacent cells of the same filament in 
Zygnema and Spirogyra be founded on correct observation, all 
idea of sexuality of the filaments must be abandoned in these 
cases. 
Bibliography of the Zygnemacee. 
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Bot. & Phys. Mem. 1853, pp. 281—290.) : 
Prinasueim. ‘Ueber Keimung der ruhenden Sporen, und über eine Form 
beweglicher Sporen bei Spirogyra.” Flora, 1853, Nos. 30, 31. (1 pl.) 
Irziasonn. “Ueber den männlichen Geschlechtsapparat bei Spirogyra.” Bot. 
Zeitung, 1853, pp. 201 & 217. (1 pl.) : > 
Irzicsoun. “Die Fruktifikation der Mougeotia.” Bot. Zeitung, 1853, p. 681. 
Coun. Untersuchungen über die Entwickelungsgeschichte der mikroskopischen 
; Algen und Pilze, 1854. (1 pl. of Zyg.) S 
NiGELI und Cramer. Pflanzenphysiologische Untersuchungen. Heft 1, 1855. 
(2 pl. of Spirogyra.) F 
Prinesnem. Zur Kritik der Untersuchungen über das Algengeschlecht, 1856. 
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America, 1872. (4 pl. of Zyg.) 
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new genus Gonatonema, 1878. (1 pl.) 
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Zyg. 
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Henfrey's Micrographic Dictionary, ed. 4, 1883. 
Cooxr. British Freshwater Algz, 1883. (16 pl. of Zyg.) 
