9i0 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Count found the frustules of diatoms belonging to a number of 

 distinct species and genera, the dominant form being a beautiful 

 Thalassiosira, probably T. NordensTcidlclii Clove. 



Diatoms of Franz-Josefs Land.*— A. Grunow has had the oppor- 

 tunity of examining a number of diatoms from Franz-Josef's Land, as 

 well as from an ice-block west of Matotschkin-Scharr. They differ 

 from the diatoms at present known from arctic regions, and a number 

 of new species are described. The fresh-water forms are very 

 different from those obtained from deep soil, and much more closely 

 resemble known arctic forms. 



Structure of Diatoms from Jutland " Cement-stone." f— W. Prinz, 

 whose previous researches on this subject we have recorded, has, in 

 conjunction with Dr. E. Van Ermengem, undertaken a more elaborate 

 investigation, princij)ally on Coscinodiscus Oculus Iridis and Trinacria 

 regina (and allied forms from the London clay), making sections by the 

 grinding method previously described. The details and results are 

 embodied in an exhaustive paper, which will be read with great appre- 

 ciation by all who are interested in the subject. The plates are 

 necessary to properly follow the paper, and these cannot unfortunately 

 be reproduced here. 



The short result of the authors' investigations is that not only 

 do the valves of the diatoms examined consist of two laminae, in the 

 outer of which are hexagonal or circular areolae, but that the exterior 

 lamina is wholly made up (in the diatoms with hexagonal markings) 

 of the honeycomb structure, entirely open at the top of the alveoli, 

 and that the interior lamina only partially closes these openings, 

 being itself perforated by circular holes at the bottom of each of the 

 hexagons, which holes are bounded by a wall like a section of tube, 

 which projects a little way through the lamina both outwardly and 

 inwardly. 



Prof. A. Grunow, ante, p. 436, stated his opinion to be that the 

 perforations (which he agreed were proved by the authors to exist in 

 the diatoms from Jutland cement-stone and London clay) were due to 

 the fact that the diatoms had begun to undergo dissolution, the delicate 

 closing membranes of the alveoli disappearing first of all. The 

 authors consider | that this dissolution is disproved by the fact of the 

 preservation (in the cement-stone) of the delicate markings oiJaniscMa 

 and the existence of young incompletely silicified valves of Coscino- 

 discus, whilst the diatoms from London clay were covered with pyrites 

 soon after death and before dissolution could have set in. 



Dr. L. Errera, in a subsequent discussion,§ raised the question 

 whether, notwithstanding the absence of siliceous membranes covering 

 the perforations (which, however, he did not consider disproved), 

 there might not exist in the living diatom a cellulose membrane 



* Denkschr. K. K. Akad. Wiss. Wien, xlviii. (1884). See Bot. Centralbl., 

 xix. (1884) p. 65. 



t Ann. Soc. Belg. Micr.— Mem., viii. (1883) pp. 7-74 (4 pis. and 6 figs.). 

 J Bull. Soc. Belg. Micr., x. (1884) pp. 79-82. 

 § Ibid., pp. 82-6. 



