ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 21 :'»: 



upon. Passing on to Rhiporephalus Phoenix, the authors break up that 

 species into three varieties — typica, brevifolia, and longifolia ; and refer 

 to the last of these a remarkable specimen from Florida, which bears 

 flabella nearly 5 cm. long. 



Microspores of Diatoms.* — G. Karsten has made some interesting 

 and important observations on the so-called " microspores " of a new 

 species of plankton diatoms — Oorethron Valdivicc — brought home by the 

 German Deep Sea Expedition from the Antarctic Seas. It is a common 

 species, and was found in a normal condition, with microspores as 

 well as with plentiful auxospores. The cell-contents were seen 

 divided in multiples of 2 up to 128, and consisted of globular cells sur- 

 rounded by a protoplasmic membrane. The author succeeded in finding 

 stages of division from 16 to 32, in which nuclear spindles were just 

 being formed. The nuclei all divide simultaneously, and the chromato- 

 phores also divide. Eventually, these globular cells escape, and are 

 found hanging in masses entangled among the spines of mature 

 individuals. It has been suggested that these cells in another genus 

 (Rhizosolenia) are either true spores which grow into a mature 

 individual, or that they are male cells which copulate with other cells, 

 and thereby occasion the formation of auxospores. The author, how- 

 ever, finds that they are in reality neither the one nor the other. The 

 microspores of different origin unite in pairs and form a zygote, the 

 further development of which is traced as far as possible on the material 

 at the author's disposal, and the different stages are described and figured. 

 The process may be summarised briefly. Gametes from two mother-cells 

 unite in pairs, the zygotes increase in size and produce two daughter-, 

 cells of similar orientation. Each daughter-cell possesses two similar 

 nuclei. During the gradual development of the upper end of the cell, 

 the nucleus situated at that end increases in size, while the lower nucleus 

 diminishes. By the time the shell, or frustule, begins to form, the small 

 nucleus has disappeared. After the crown of notches has been formed 

 on the upper shell, the young plant bursts through its shell, and stretches 

 out to form a complete Corethron Valdivice. The bristles, the second 

 shell, and the girdle develop gradually, and the normal length is attained 

 by elongation of the girdle bands, while the diameter may be increased 

 by the formation of auxospores. The main interest of the above 

 described development lies in its parallelism to that of the Desmid 

 zygote, which is discussed ; and new points of relationship are brought 

 forward. 



Diatoms of the Montagne Noire, Pyrenees.! — J. Comere has ex- 

 amined a collection of diatoms made in the basins and canals which 

 supply water to the Canal du Midi. The results of the six different 

 gatherings are presented in tabulated form, and include sixty-six specks. 

 Of these, one only appears to be new for the south-west of France — 

 i. e. Cymbella anglica — which occurs abundantly in most of the samples. 

 The entire collection shows a mixture of epiphytic and limnophilous forms, 

 such as Cocconeis, Rhoicosphenia, Epithcmia, etc. ; and of forms which 



* Ber. Deutsch. Dot. Gesell., xxii. (1904) pp. 544-54 (1 pi.). 

 t Bull. Soc. Bot. de Fiance, li. (1904) pp. 338-45. 



