ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
561 
and increase enormously in April and May. Among these spring 
species are Diatoma tenue var. elongatum , Synedra delicatissima , Aster io- 
nella gracillima , and Fragilaria crotonensis ; and meantime Melosira 
wanes almost to disappearance. He gives figures showing for four 
months a quantitative estimate of the Plankton (after Hensen’s method), 
as far as Bacillariacese and the like are concerned. The quantity of 
Asterionella increased five times in 13 days, of Diatoma tenue six times in 
10 days. In a litre taken in the month of May from the depth of one 
metre there were 54,500 chains of Diatoma tenue , 4500 individuals of 
Synedra delicatissima, 2500 individuals of S. longissima, 500 individuals 
of S. ulna, 1000 bands of Fragilaria crotonensis , 3500 stars of Asterionella 
gracillima, 700 balls of Uroglena volvox, 4000 colonies of Dinobryon 
stijpatum , 1500 colonies of D. divergens , 250 balls of Eudorina elegans. 
Structure of Protococcoideae.* * * § — Prof. R. Chodat has further studied 
the structure of Golenkinia, which has a parietal chromatophore and an 
amyliferous pyrenoid. It is reproduced by hemizoospores, spores, and 
autospores, and it occurs also in a palmelloid condition, in which it gives 
birth to four ciliated zoospores. Another new genus of Protococcaceee is 
described, Tetraceras (afterwards changed to Lagerheimia f), reproduced 
by autospores which form small colonies of 4 or 8 individuals, and 
occurring also in a palmelloid condition which produces fusiform zoo- 
spores. It is probably a condition of Scenedesmus. 
In another paper J M. Chodat describes the mode of formation of the 
spores of Baphidium Braunii, and the structure of Actinastrum, and 
proposes another new genus of Protococcaceae, Tetrastrum, allied to 
Lagerheimia. 
M. Chodat § further confirms his previous statement that Pleurococcus 
vulgaris occurs in the following conditions, — unicellular, pleurococcus, 
stichococcus, cystococcus, and microthamnion. The last is a branched 
filamentous form. 
Genera of Diatoms. — M. J. Tempere |j completes his revision of the 
genera of diatoms with a few additional names, and appends the following 
diagnosis of the new genus Cleveia Pant. : — Frustulis convexis, a latere 
primario visis late lanceolatis, cum structura striata asymmetrica ornatis ; 
a latere secundario maxime convexo-rectis cum structura medio biserialiter 
punctatis et ad latera cum loculamentis alternate majoribus et minoribus 
vestitis. 
Dr. H. Van Heurckl’ gives a synopsis of all known genera of diatoms, 
recent and fossil, 191 in number. 
Reproduction of Diatoms.** — Mr. J. N. Coombe gives a careful 
resume of the observations and theories of various observers on this 
subject. His own observations confirm the statement that in several 
species of diatoms, both marine and freshwater, the endochrome breaks 
up, under certain conditions, usually of deficient nutrition, into globular 
* Arch. Sci. Phys. et Nat., xxxii. (1894). Cf. this Journal, ante, p. 212. 
f La Nuova Notarisia, vi. (1895) pp. 86-90 (12 figs.). 
X Bull. Herb. Boissier, iii. (1895) pp. 109-14 (2 figs.). 
§ Arch. Sci. Phys. et Nat., xxxiii. (1895) pp. 196-7. 
|| Le Diatomiste, ii. (1895) p. 162. Cf. this Journal, 1893, p. 672. 
1 Tom. cit., pp. ISO-6. ** Tom. cit., pp. 152-9, 165-80 (4 pis.). 
