26 



HARDWICKE'S SCIENCE -GOSSIP. 



newly-iuveuted engiscope (or aplanatic microscope), 

 the performance of metal reflectors (amiciaii reflect- 

 ing engiscope), and achromatic objectives are also 

 discussed. — E. K.) 



Within Navicula Amphisbana he considered the 

 coloured substance as an ovary, and took the lighter 

 cysts appearing therein as polygastric stomach-sacs. 



In the year 1S3S appeared the great work by 

 Ehreuberg "Die lufusiousthierchen als vollkom- 

 mene Organismeu," in which he still adhered to 

 the animal nature of the Diatomaceie, and fancied 

 he saw openings or mouths, stomach-cells, sexual 

 organs, and foot-like projections. The filamentous 

 forms he compared to Polypi stems. 



Since the first attempts to bring the Diatoms 

 into several genera, the outward form of the shell- 

 covered body, the manner in which the single indi- 

 viduals are united, and the presence or absence of 

 stipes whereby they are attached, have been prin- 

 cipally taken as the foundation of classifications 

 since Ehreuberg introduced also the presence or 

 absence of shell-openings for the distinction of 

 genera ; but the main groups were arranged accord- 

 ing to the presence or absence of stipes, a mistake 

 which caused the author to mention Lyugbye's 

 Biatoma arciiatum not only as two different species, 

 but also under two different genera, viz. as Tessella 

 catena, and Striatella arcuata. His 15i species, 

 contained in the work already mentioned, are 

 mostly accompanied with very carefully drawn 

 figures. In 1839 he published, in the Proceedings 

 of the Berlin Academy of Sciences, " The Formation 

 of the European, Libyan, and Arabic Chalk Rocks, 

 and the Chalk-marl from Microscopic Organisms." 

 In this communication he described the new genera 

 Coscinodiscus and Dictyocha. [The latter genus is 

 now removed from the Diatomacese, with which it 

 has no afiinity.— E. K.] In 1840 Ehreuberg dis- 

 covered that many of the fossil forms were still 

 living in sea-water (also published in the Proceed- 

 ings of the Berlin Academy). He also published 

 the new genera Amphitetras, Ceratoneis, Grammato- 

 phora, Lithodesmmm, Podosira, Triceratium, Tri- 

 podiscus, and Zygoceros. In the same year a further 

 communication contained a description of about 100 

 new species ; and the genera Amphipentas, Campy- 

 Jodiscus, Discoplea, and Himantidium. He also pub- 

 lished, in ISiO, his work on the extent and influence 

 of microscopic life in North and South America. 

 Professor Bailey had already, in 1838, given the 

 outlines of American Bacillarige in Sdliman's 

 " Journal of Science and Art," and had also espe- 

 cially reported on the fossil forms of North 

 America. 



Ehreuberg received abundant material from North 

 America, and at the same time he received contri- 

 butions from South America through his brother, 

 Carl Ehreuberg. He also obtained earth from 

 various parts of the Continent, which was brought 



to Europe in the transportation of lumber {Pfiunzen- 

 transport), so that he obtained a view of the forms 

 from forty-four different localities in America, from 

 the Falkland Islands to Kotzebue Sound. 



In the same year in which Ehrenberg's great 

 work on the Infusorise appeared, A. de Brebisson 

 had diligently studied the Algse of his neighbour- 

 hood (Falaise), the results of which he published in 

 his " Considerations sur les Diatomees," in which 

 he introduces the genera Cymhophora and Epithemia. 



About this time Greville (in Hooker's " British 

 Flora ") and Harvey (in the " Manual of British 

 Algse") became co-workers among the Diatomacese. 

 The latest discoveries appeared to have been quite 

 unknown to them ; at least, they have no influence 

 on their labours. 



Ralfs has furnished the most recent work on 

 British Diatoms in a single monograph, which is 

 printed and accompanied with figures in the twelfth 

 vol. of "Annals and Magazine of Natural History." 



Rail's excels his predecessors in the correctness 

 of his descriptions ; but his figures are mostly crude 

 (with the exception of those of Amplutetras, Bid- 

 diilphia, and Isthmia). 



F. K. 



CEAPTERS ON CUTTLES. 



No. 3. 



Br W. H. Booth. 



WE have now arrived at the last family of sec- 

 tion B, the Spirulidce. The little Spirula, 

 or Ram's-horn, is a shell familiar to most of us, 

 though we may not be acquainted with the animal 

 that formed it. Many of these shells are brought 

 by the Gulf Stream and strewed along the coast of 



Fig. 20. Ammonites amaltheus, showing foliation of chambersj 



the Peninsula, whilst a few find their way to our 

 own coast. For a long time the animal to which 

 this shell belonged had not been discovered, and it 



