ZOOLOGY AND BOTANY, MICKOSOOPYj ETC. 627 



phyton under Phseopliyceas, as well as Syncrypta, usually placed under 

 Volvocineae. The ChloropliyceaB are divided into ConfervoideEe, Sij)lione8e, 

 Protococcoidese, and Conjugatge ; and the isogamous Confervoidese again 

 into Chsetoplioracese, Cladophoracete, Trentepohliacese, and TJlvacese. 

 The Protococcoidege are again divided into VolvocineEe, including the 

 new genus Cylindromonas, and Palmellacese, with which the Protococcaceje 

 are united. Under the Protococcacese is placed the new subfamily 

 Coccacese which includes a number of forms regarded by the author and 

 others as stages in the development of higher algse. A number of new 

 species and varieties are described. Some further details are given in 

 another paper.* 



-Hauck and Ricliter's Phycotheca universalis. — Three parts of 

 this valuable publication are now issued. Each contains a specimen of 

 50 species belonging to every class of algae, many of these being rare 

 and difficult to obtain. The synonyms of each species are given in 

 detail, and the locality whence the sj)ecimen was obtained. 



Venetian Chlorophycese.t — The third part of De Toni and Levi's 

 ' Flora Algologica della Yenezia ' is devoted to the Chlorophycese, the 

 authors following almost entirely the classification of Eabenhorst. The 

 members of each genus, as well as of the larger groups, are arranged in 

 an analytical key. 



Chsetoceros.J — Herr F. Schiitt describes the structure of this genus 

 of Diatomace^, of which several species are at times exceedingly 

 abundant in the Baltic, floating free on the surface of the water. The 

 cell-wall consists usually, as in Melosira, of only three pieces, the two 

 valves and a single girdle, and the genus is distinguished from all others 

 by the very long horns, a pair of which spring from each end of each 

 cell. They are not above 1/20 the diam. of the cell, but many times as 

 long. They are continuations of the eelJ.-wall, and are, like it, strongly 

 silicified, the cell-contents being in unbroken communication ; and tbey 

 may even contain chromatophores. The separate cells which result from 

 the division of a single mother-cell usually remain for a time attached to 

 one another in chains, the mucilaginous substance which connects them 

 together being apparently formed between the horns. In the process of 

 cell-division the horns do not begin to make their appearance, as small 

 papillae, until the young cells have nearly separated from one another. 



Like m^iU^ other genera of diatoms Chsetoceros is characterized by the 

 formation of " internal cells " or resting spores, formed singly in the 

 mother- cells. They are formed by the contraction of the contents of the 

 mother-cell, which retreat from the cell-wall and round themselves off, 

 secreting at the same time a new cell-wall which is provided with spines 

 or protuberances. These are not, like the horns, hollow, but are solid 

 silicified rods. The horns of the mature cell vary greatly in form and 

 size in different species of the genus, and even within the same species. 



Varieties of Aulacodiscus.§ — Mr. J. Eattray supplements his mono- 

 graph of this genus || by a descrijDtion of abnormalities which occur in 

 the different species in the following points : — (1) Outline : — the ordinary 



* Oesterr. Bot. Zeitschr., xxxviii. (1888) pp. 41-4, 87-9, 114-7, 149-51. 

 t De Toni, G. B., e D. Levi, ' Flora Algologica della Venezia. Parte terza, Le 

 Oloroficee,' 206 pp., Venezia, 1888. 



X Bot. Ztg., xlvi. (1888) pp. 161-70, 177-84 (1 pi.). 



§ Journ. of Bot., xxvi. (1888) pp. 97-102 (1 pi.). || This Journal, ante, p. 337. 



