HARDWICKE'S SCIENCE-GOSSIP. 



77 



mand ; and now we shall see what this reservoir is 

 and by what means it is replenished. When a toad 

 is hastily seized, or even quickly pursued, it often 

 voids a considerable quantity of water which is 

 generally but erroneously supposed to be the urine. 

 This water is limpid and pure, containing no traces of 

 the usual component elements of the urinary secretion. 

 I have tasted it and found it to be like pure water. 

 It is contained in a sac, which has also been mis- 

 takenly believed to be the urinary bladder. This is 

 the reservoir to which I have alluded. When, there- 

 fore, the toad is happily placed in a damp atmosphere, 

 or in water, the skin absorbs a quantity of water 

 which there is every reason to believe is secreted in 

 the bladder just mentioned, where it is kept in store 

 until the dryness of the skin requires a supply for 

 the purpose of respiration, when it is again taken 

 up and restored to the surface by which it had been 

 first absorbed. 



(To be continued.) 



THE EARLY HISTORY OF THE 

 DIATOMACE/E. 



By F. Kitton, Hon. F.R.M.S. 



THE study of the minute forms of animal and 

 vegetable life appears to have been enthu- 

 siastically pursued by the philosophers who lived 

 during the latter half of the seventeenth century. The 

 names of Leeuwenhoek, Swammerdam, and Hooke 

 are still "household words" with the microscopic 

 student, but the very imperfect microscopes of that 

 period rendered it impossible for them to discover 

 the nature of those minute forms of life which we now 

 call diatoms. 



According to Ehrenberg the first diatom observed 

 was Synedra ulna (Leeuwenhoek in "Philosophical 

 Transactions," 1703, pi. 1, fig. 8, and again de- 

 tected by Joblot in 1 714-16, and figured in his 

 " Observations faites avec le Microscope). We have 

 referred to the paper* and figures of the former 

 writer, and are unable to find any figure or descrip- 

 tion that agrees with that genus, or indeed with any 

 diatom. Joblot's work we have never seen. A few 

 pages further on is a paper (author not given) en- 

 titled "Remarks on M. Leeuwenhoek's Observations 

 on Green Weeds and Animalcula." 



In this paper is the following paragraph : 

 " In my observations on these stalks (roots of 

 Lemna, called by the writer Lens palustris), I often 

 saw adhering to them, and sometimes separate in 

 the water, many pretty branches composed of rectan- 

 gular oblongs and exact squares, which were joined 

 together as in fig. 19 (our fig. 50), which I drew 

 as exactly as I could from one of them. There are 

 often twenty or more of these figures in one branch, 



* "Concerning Green Weeds growing in Water, and some 

 Animalcula found about them." By M. Leeuwenhoek, 1703. 



which generally adheres at one end to the stalks of 

 the plant, and I think it remarkable that these 

 rectangular parallelograms are all of the same size, 

 the longest side not exceeding one-third of a hair's 

 breadth, the squares being visibly made up of two 

 parallelograms joined lengthwise. They seem very 

 thin, and the texture of every one is nearly the same." 

 This description is almost sufficient to enable a 

 diatomist to recognize not only the genus but the 

 species, and the figure which we here reproduce 

 leaves no doubt that the above form is the same as 

 that now known as Tabellaria flocculosa (fig. 50). It is 

 somewhat surprising that Ehrenberg should have over- 

 looked this figure ; possibly he found the reference to 

 Synedra ulna in Joblot's treatise, and had not seen 

 the Transactions. We have been unable to discover 

 any figure or description of any other species of 

 diatom until the year 1745, when William Arderon 

 detects the "oat-like animal" associated with his 

 " hair-like insect " (Oscillatoria). Both are described 

 with considerable minuteness, and illustrated by 

 several figures in Baker's "Employment for the 

 Microscope." This "oat-like animal" was un- 

 doubtedly a Navicula, probably N. sphcerophora or 

 N. amphisbana. 



Fig. 50. — Tabellaria flocculosa , about 130 diameters. 



The few forms of Diatomacece observed up to the 

 end of the eighteenth century were considered to be 

 either infusory animalcules or confervas. 



Although many papers appeared from time to time 

 in various scientific publications, no work solely de- 

 voted to the Infusoria appeared until 1766, when 

 Midler's work was published. More than fifty years 

 had elapsed when D. Christian Gottfried Ehrenberg 

 published his great work, "Die Infusions*hierchen 

 als Volkommene Organismen. Ein Blick in das 

 Tiefere organische Leben der Natur," 1838, in 2 

 vols, folio : one of text containing 547 pages ; the 

 other of plates, of which there are 64 beautifully 

 engraved and coloured. The text consists of: (1) The 

 Dedication to Frederic William, Crown Prince of 

 Prussia ; (2) a long and interesting preface, in which 

 are given complete directions for obtaining and pre- 

 paring the Infusoria for observation. This is followed 

 by the description of the various genera and species 

 (in Latin, French, and German) of Infusoria, seventy- 

 six pages and nine plates being devoted to the 

 Diatomacese. 



Professor Ehrenberg included in his family Bacil- 

 laria not only some of the Desmidese, but also some 

 forms of Animalcula. This may be accounted for, 

 as he to the last contended for the animality of the 



