266 MR. W. WEST ON SOME FRESHWATER 
Class CONJUGATS. 
Ord. ZYGNEMACE. 
5. ZyaNeMwa (ZYGOGONIUM) PACHYDERMUM, nov. sp. (Pl. 
XIII. figs. 1-16.) 
Z. cespitibus intricatis; filis flexuosis (et interdum genu- 
flexuosis) dense intricatis, hine inde ramulis brevibus irregulari- 
busque cellularam 2-6; cellulis vegetativis diametro 2-23plo 
(sepe 3plo) longioribus (rarius equalibus); membrana cellu- 
larum crassa vel crassissima; zygosporis in tubo conjugationis 
brevi inter cellulas sitis, subglobosis, subellipsoideis, plerumque 
irregularibus (sepe constrictis); membrana zygosporarum cras- 
sissima, irregulariter lamellosa ; azygosporis globosis subglobo- 
sisque, zygosporis similibus sed membrana tenuiore. 
Crass. cell. veget. 16-23 » (usque ad 26 » et plerumque 20 p); 
crass. membr. cellularum 1°5-5°5 x; long. zygosp. 25°5-33 p 
(usque ad 40); lat. zygosp. 19-26 » (usque ad 30,); crass. 
membr. zygosp. 2°5-6°5 p; diam. azygosp. 23-26 »; crass. membr. 
azygosp. 1°9-3°8 p. 
Hab. In mud, warm stream, crater of Grande Soufriére, 
Dominica. No. 883; also in no. 908, and sparingly from 
no. 882.—This also occurred, without zygospores, on old wall, 
Roseau, Dominica. (1-8-92.) No. 473. 
This species has a thick membrane which at first sight reminds 
one of a Lehizoclonium or a large species of Conferva, the some- 
what irregular filaments with short branches resembling the 
former especially. The many examples of conjugation examined 
were all scalariform, the zygospores completely filling the short 
conjugating-tube, their variability being remarkable, Spores 
were seen (figs. 9-10) which were undoubtedly azygospores, and 
these were regular in shape. One example was noticed where 
the zygospore was double. The material was preserved in weak 
spirit; but the two chromatophores were in most examples 
distinct and in their normal position. 
Var. CONFERVOIDES, nov. var. (Pl. XIV. figs. 1-6.) 
Var. cellulis tenuior, diametro plerumque 1-14plo (rarius 
23 plo) longioribus. 
g 
Crass. cell. veget. 10-13 p. 
Hab. In mud, warm stream, crater of Grande Soufri¢re, Do- 
minica. No. 883. Intermingled with the typical form, but not 
so abundant. 
