•476 SUMMARY OF CURRENT RESEARCHES RELATING TO 



remains in connection with the girdle, and that the girdle consists of a 

 simple hollow cylinder, while the valves show a strong incurving on the 

 side turned towards the girdle. Thus the connection between valve and 

 girdle is a very loose one. For a final explanation of the gelatinous 

 external band investigation of other species is necessary. It seems to 

 be absent in G. boreale and G. constrictum, while in G. decipiens, the 

 species principally studied, it was not always present. As regards the 

 object of the gelatinous band, the author is of opinion that it is con- 

 nected with the floating apparatus, and indeed bears the same relation 

 to the external rays of Ghcetoceras as the silk of an umbrella does to the 

 ribs. 



Membrane of Diatoms.* — L. Mangin has studied the constitution 

 •of the membrane of diatoms, and finds that it is not composed, as has 

 been believed, of cellulose or of something akin to that substance ; but 

 that it responds, on the other hand, to pectic reagents, and is therefore 

 clearly composed either of pecten or of substances closely akin to it. 

 Diatoms which are fresh or have been preserved in alcohol do not 

 respond well to the action of stains, and it is necessary to prepare the 

 material by the use of certain salts (iron-alum, ammonium vanadate, etc.), 

 and stain with old hgematoxylin-alum. 



Other methods of preparation are described also, and the use of 

 ruthenium and of old hamiatoxylin-alum is recommended previous to 

 mounting in Canada balsam. Comparison is drawn between the con- 

 stitution of the membrane of Diatoms and that of Peridinieas, in which 

 the substance is almost pure cellulose. The author finds that calcination 

 is a considerable aid to the study of the niinute structure of the valves, 

 but the process can only be applied to bottom forms, as plankton 

 diatoms are too delicate. The staining of plankton is an important 

 factor in a study of their structure, and has enabled the author to 

 correct certain erroneous views concerning Ghcetoceras and other genera. 

 He divides Ghcetoceras into two groups, which he briefly defines, and 

 into one of which he sinks Schiitt's genus Peragallia. A paper con- 

 taining more details on the subject is promised shortly. 



New England Desmids.f — J. A. Cushman records 49 species of 

 Closterium from New England, 19 of which have not been noted before 

 from that district. One new species, G. Novce-Anglice, is described : it 

 is one of the longest species of the genus, and is near G. Calamus 

 Playfair. A short diagnosis and measurements are given for each 

 record, as well as references to literature, and reliable plates. In a short 

 introduction the author describes the principal characters of the genus 

 and of the two groups into which it is divided. 



Origin of Californian Petroleum.^— A. M. Edwards discusses the 

 origin of petroleum in California, and states his reasons for supposing 

 that the connection observed between deposits of marine diatoms and 

 asphalt and petroleum indicates that petroleum rock-oil and asphalt are 

 products of the decomposition of beds of marine diatoms. 



* Comptes Rendus, cxlvi. (1908) pp. 770-3. 



t Bull. Torrey Bot. Club, xxxv. (190S) pp. 109-34 (3 pis.). 



X Nuov. Notar., xix. U908) pp. 72-78. 



