ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 491 



graphy ; it then proceeds to a complete index of the Desmidiaceas arranged 

 under the specific names, every published figure being referred to. An 

 index of the genera completes the work. It will be indispensable to 

 the algologist as a work of reference. 



Minute Structure of Diatoms.* — In a paper on this subject by Mr. 

 A. A. Eliot Merlin, the most interesting point is the discovery that the 

 eye-spot plate of a Biddulphia (J5. reticulata Roper ?) contains several 

 perforations (ten have been counted) in place of the usual single central 

 perforation. This is the first recorded instance of any multiple eye- 

 spot structure in the Diatomaceae. The structure of the outer covering 

 cap resembles that of Coscinodiscus Asteromphalus. Mr. Merlin suggests 

 the use of averted vision for the observation of extremely minute 

 structures, the value of this method being well known to telescope 

 observers. 



Formation of Auxospores in Diatoms. f — Herr G. Karsten recounts 

 some further observations on this subject. In Bhabdonema arcuatum 

 the process is simply a modification of cell-division ; the daughter-cells 

 throw off the old valves which have become two small, and, after rapid 

 enlargement, invest themselves in new ones. In B. adriaticum one of 

 the daughter-cells does not increase in size, and is finally ejected from 

 the cell-plasm. In the forms endowed with motion — Cocconeis, Suri- 

 rella — two individuals take part in the formation of one or two auxo- 

 spores, formed from the union of their contents. In two species of 

 Cymatopleura two auxospores appear to be always formed from the con- 

 tents of two mother-cells. This is also the case with by far the larger 

 number of ground-species, — Naviculese, Cymbelleae, Achnantheae, and 

 Nitzschieae. Each mother-cell divides into two daughter-cells ; and the 

 four then conjugate in pairs, the two auxospores being formed from the 

 two zygotes. The most essential point in the formation of an auxospore 

 is that the cells increase in size. 



Herr Karsten regards the desmids as the nearest relations of the 

 diatoms. 



Wax from Diatoms. J — Herren G. Kramer and A. Spilker point out 

 the probable importance, from a practical point of view, of the oil 

 secreted in the protoplasm of diatoms. From this oily secretion a wax 

 can be obtained, resembling ozokerite in appearance, chemical compo- 

 sition, and properties. The authors suggest that the decay of the diatoms 

 gave rise to ammonium carbonate, which hydrolysed the wax ; from the 

 resulting acids carbon dioxide and monoxide and water were eliminated, 

 and ozokerite formed. Further pressure, again, converted this ozokerite 

 into petroleum ; and the theory is advanced that this is one of the most 

 important sources of the immense beds of this substance. 



Formation of Chlorophyll in the Dark by a Green Alga. § — 

 M. Radais confirms the statement of Beijerinck that Chlorella vulgaris 

 has the faculty of cell-multiplication as rapidly in the dark as in the 

 light. The spectrum of the pigment indicates that it is a chlorophyll. 



* Journ. Quekett Micr. Club, vii. (1900) pp. 295-8 (1 pi.). 

 t Biol. Centralbl., xx. (1900) pp. 257-64. Cf. this Journal, 1S99, p. 514. 

 J Ber. Deutsch. Chem. Ges., xxxii. (1899) pp. 2940-59. See Journ. Chem. Soc, 

 1900, Abstr. i. p. 73. § Coroptes Rendus, cxxx. (1900) pp. 793-6. 



