459 
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
the thallus. The term prothallium is not correctly applied to any of 
these forms. 
Polymorphism of Monostroma.* * * § — As is the case with others of the 
lower Algie, Prof. R. Chodat states that Monostroma bullosum assumes, in 
cultivation, several distinct forms, viz. a transitory or Schizochlamys form 
and a permanent “ hypnocyst ” form, in which the cells are thick- walled 
and their contents coarsely granular. These hypnocyst cells may be- 
come detached, and then give rise, by cell-division, to a “ hypnothallus” 
form, which may be sublilamentous and chroolepoid, or massive and 
expanded. From the alga in this state are produced the zoogametes. 
In its Schizochlamys condition it is scarcely distinguishable from S. 
gelatinosa. 
Euastropsis, a new Genus of Hydrodictyacese.f — An organism 
previously described as Euastrum Bichteri is made by Prof. G. Lager- 
heim the type of a new genus Euastropsis , belonging to the Hydro- 
dictyaceae, with the following diagnosis : — Coenobium libere natans, 
bicellulare ; cellulae chlorophoro laminiformi, parietali, amyligero, pyre- 
noide plerumque singulo, nucleo singulo ; multiplicatio macrozoogonidiis; 
macrozoogonidia primo ovalia, dein rotundata, ciliis vibratoriis binis, 
stigraate nullo, bipartitione succedanea contentus cellulae utriusque 
ccenobiis orta, in vesicula inclusa per rimam strati externi membranae 
exeuntia ; bina polo antico achroo conjunguntur et coenobia plura formant. 
The chief distinction between Euastropsis and Pediastrum is that in the 
former the swarm-cells unite into several daughter-colonies, the coenobe 
consisting of only two cells. It appears to form a link between Pedi- 
astrum and Tetraedron. 
The life-history of Tetraedron minimum, is also followed out in detail. 
Pediastrum is, in all probability, derived genetically from Tetraedron. 
Reproduction of Aphanochgete.J — M. J. Huber records the observa- 
tion, in Aphanochsete repens , of a sexual mode *of reproduction, through 
impregnation of nearly spherical ciliated oospheres by smaller pear- 
shaped four-ciliated antherozoids. Both bodies are invested in a hyaline 
vesicle, and the movements of the oosphere are but very feeble. A 
diminution of light appears to favour the formation of zoospores at 
the expense of sexual reproduction. This is the first instance in which 
a conjugation of motile heterogametes has been observed in the 
Confervoideae. 
Development of Pediastrum.§ — Prof. R. Chodat and M. J. Huber 
have experimented on the cultivation of that very variable species, 
Pediastrum Boryanum, in various nutrient solutions, and find the pro- 
duction of the so-called varieties to be largely due to differences in 
nutrition. They suggest caution in the publication of new species or 
varieties where the author is not able to follow out the life-history of 
the organism. 
* Bull. See. Bot. France, xli. (1895), Sess. Extraord., pp. cxxxiv.-xlii. (1 pi.). 
f TromsoMus. Aavsheft, 1894, 24 pp. and 1 pi. See Bot. Centr., 1895, Beik., p. 2. 
X Bull. Soc. Bot. France, xli. (1895) Sess. Extraord., pp. xciv.-ciii. (1 pi.). 
§ Bull. Soc. Bot. Suisse, 1895, 14 pp. and 1 pi. 
