266 ME. W. WEST ON SOME FEESUWATEB 



Class Conjugate. 



Ord. ZVGNEMACEiE. 



5. Ztgnema (Ztgogonitjm) pachtdermtjm, nov. sp. (PI. 

 XIII. figs. 1-16.) 



Z. csespitibus intricatis ; fi.lis flexuosis (et iDterdum genu- 

 flexuosis) dense intricatis, hinc inde ramulis brevibus irregulari- 

 busque cellularum 2-6 ; cellulis vegetativis diametro 2-2|plo 

 (ssepe 3plo) longioribus (rarius sequalibus); membrana cellu- 

 larum crassa vel crassissima; zygosporis in tubo conjugationis 

 brevi inter cellulas sitis, subglobosis, subellipsoideis, pleruiiique 

 irregularibus (saepe constrictis) ; membrana zygosporarum cras- 

 sissima, irregulariter lamellosa ; azygosporis globosis subglobo- 

 sisque, zygosporis similibus sed membrana tenuiore. 



Crass, cell, veget. 16-23 /z (usque ad 26 /i et plerumque 20 ju) ; 

 crass, membr. cellularum l*5-5*5 /i ; long, zygosp. 25'5-33 \x 

 (usque ad40/j); lat. zygosp. 19-26 /u (usque ad 30 /x); crass, 

 membr. zygosp. 2*5-6'5 \x ; diam. azygosp. 23-26 /i ; crass, membr. 

 azygosp. l"9-3'8/Lt. 



Hah. In mud, warm stream, crater of Grande Soufriere, 

 Dominica. No. 883; also in no. 908, and sparingly from 

 no. 882. This also occurred, without zygospores, on old wall, 

 Eoseau, Dominica. (1-8-92.) No. 473. 



This species has a thick membrane which at first sight reminds 

 one of a Ilhizoclonium or a large species of Conferva, the some- 

 w^hat 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 

 w'ere 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. coNFERVOTDES, nov. var. (PI. XIV. figs. 1-6.) 



Var. cellulis tenuior, diametro plerumque l-l|plo (rarius 

 2|pl() longioribus. 



Crass, cell, veget. 10-13 jjl. 



Hah. In mud, warm stream, crater of Grande Soufriere, Do- 

 minica. No. 883. Intermingled with the typical form, but not 

 80 abundant. 



