ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 489 



membrane, etc., and then proceeds to relate how he found, after some 

 days, a number of hat, three-cornered cells which clearly belonged to 

 Tetraedron, intermixed with the Oocystis. Finding, however, that the 

 TetraMron cells increased without any appearance of division, he 

 examined more carefully, and discovered that they formed the resting- 

 cells of the Oocystis. He describes the manner in which these arise 

 from the original Oocystis, and figures their different stages. The 

 author kept cells of the Tetraedron stage all the winter under cultiva- 

 tion, and watched them in the following April produce new Oocystis 

 cells, two arising from each Tetraedron cell. The Tetraedron stage arises 

 in consequence of certain external influences which are not definitely 

 known yet ; but the author thinks it may be due to a concentration of 

 salt in the stagnant pools where the algas grow. 



Cladophora and Monostroma.*— F. S. Collins describes four new 

 species of Cladophora : two from California, and one each from 

 Bermuda and Jamaica. The types of three of them are preserved in 

 the author's own herbarium. 



F. S. Collins publishes f also some interesting notes on Monostroma, 

 in which he gives a short historical sketch of the genus, and then 

 discusses species-limits, alluding to criticisms of his own work by 

 Jonsson. He claims that a distinguishing character between M. Lactuca 

 and M. GreviUei lies in the difference of their fertile fronds, as dis- 

 covered by Kosenvinge. In M. GreviUei the membrane of the fertile 

 portion of the frond becomes thicker and more gelatinous, the cells 

 elongate vertically to the surface of the frond, and finally assume the 

 palisade form characteristic of M. fuscum, though on a smaller scale. 

 As the spores are discharged the membrane melts away, and there is 

 nothing of the persistent empty tissue shown in M. Lactuca. Speci- 

 mens of M. GreviUei in this condition have been distributed in Phyc. 

 Bor.-Americ, No. 1467. Finally, a new form, varians, is described for 

 M. orbiculatum. 



Fossil Algae.} — A. Rothpletz writes on algse from the Silurian 

 strata of Gotland and Osel. He regards the genus GirvaneUa of 

 Nicholson as being probably allied to Codiaceas. It occurs in the 

 Lower Silurian, and is distinguished from the calcareous nodules of the 

 Alpine Trias by a complete absence of differentiation in its tissues. 

 The latter are placed by the author in a new genus, Sphserocodium. 

 The genus Solmopora is regarded as being allied to Lithothamnium. 

 The sporangia of S. yotlandica are cylindrical, and occur isolated in 

 the sterile tissue, as in Archseolithothamnium. The Jurassic species 

 recorded from England is excluded from Solmopora and placed by itself 

 in a special genus Solenoporella. 



Observations on Diatoms. § — L. Mangin publishes the results of 

 some observations he has made on diatoms. His paper is divided into 

 four sections : (1) Chemical constitution of the membrane ; (2) growth 

 of the membrane ; (3) methods of coloration of the membrane ; (4) 



* Ehodora, xi. (1909) pp. 17-20 (1 pi.). t Tom. cit., pp. 23-6. 



\ K. Svensk. Vetensk. Akad. Handl., xliii. (1908) 25 pp., 6 tabs. 

 § Arm. Sci. Nat., ser. 9, viii. (1908) pp. 177-219 (figs, in text). 



