HARDWICKE'S SCIENCE-GOSSIP. 



107 



the same species of diatom, according to its state of 

 development, — individuals possessing 



(1) Two valves, a connective, and a nucleus") 



(fig. 75). _ t Simple 



(2) Two valves, two connectives, and a C state. 



nucleus (fig. 71). ) 



(3) Two valves, two connectives, and ") 



two nuclei (fig. 71). States of 



(4) Four valves, two connectives, and (deduplication 



two nuclei (figs. 73 and 74). | more or less 



(5) Four valves, four connectives, and | advanced. 



two nuclei. J 



Sometimes the external connective is fragile, and is 

 detached spontaneously. This is a fact that must be 

 taken into account. 



It is also well to note that the protoplasm of the 

 primordial utricle generally moves to the interior of 

 the siliceous envelope, first at the commencement of 

 the deduplication, and again after the termination of 

 that phenomenon, dragging with it the endochrome, 

 and that these movements of the colouring matter 

 vary in character according to the families and genera 

 of the diatoms. 



When a diatom is divided into two parts by dedu- 

 plication, the endochrome is also separated into two, 

 in order that it may be equally divided between the 

 two utricles. 



Every frustulc, as we have seen, consists of an old 

 valve (fig. 71, F', fig. 72, F') originating from the primi- 

 tive frustule, and a new valve of later formation, and 

 whose connective when developed will slide in the 

 connective of the old valve. It follows from this, that 

 in the great majority of the genera of diatoms, when 

 the connective is of the exact breadth of the valves, 

 or even inferior to them in diameter, all deduplica- 

 tion must lead to a diminution of the dimension of 

 the new frustule equivalent to double the thickness of 

 a connective. The thickness of the latter being 

 known, we are able d priori to determine the size 

 any descendant of a frustule will have after a deter- 

 minate number of deduplications. The act of dedu- 

 plication, considered only in connection with the pri- 

 mordial utricle, is analogous to that which takes place 

 in the majority of vegetable cells, and we may there- 

 fore consider every series of diatoms proceeding from 

 a primitive mother-cell as forming in reality only a 

 single whole — a single plant, if you will. 



In those species which form permanent series 

 (filaments) where the frustules produced by dedupli- 

 cation never separate one from another, this is very 

 obvious, but those species in which they become new 

 frustules become detached, and live free or isolated ; 

 only the eye of the philosopher can recognize the 

 analogy. 



( To be continued. ) 



The Natterjack Toad.— The Natterjack Toad 

 may be found on the west coast, near New Brighton, 

 Cheshire, amongst the sand-hills between Midston 

 and Liscard. The eggs of this interesting and un- 

 common toad appear, in their early stage, like a 

 string of beautiful pearls. 



HOW TO MAKE AND COLOUR CASTS OF 



FISHES. 



By J. E. Taylor, F.L.S., F.G.S., etc. 



OF all the natural history objects intended to be 

 preserved, perhaps none have been hitherto 

 more difficult than fishes. Either they were pre- 

 served in spirits in glass bottles, in which case they 

 were scarcely visible in the sherry-coloured liquid, 

 or they have appeared in the stuffed state as the most 

 grotesque of caricatures. Nothing can be more 

 strongly contrasted than the supple and graceful 

 forms of fishes in their native element, and the stiff 

 and angular specimens in our museums which have 

 been "stuffed." Of all skins, those of fishes are least 

 amenable to the animal preserver. They stiffen and 

 set sooner than any other, and he is obliged often 

 to turn them out, not as he would like, but as well 

 as he can. 



Some years ago, the really fine specimens of 

 coloured casts of fishes placed in the South Ken- 

 sington Museum, under the direction of Mr. F. 

 Buckland, drew the attention of all lovers of fishes to 

 the new method of preparing specimens. Those ex- 

 hibited by Mr. Buckland are still so like life, both in 

 colour, marking, and the graceful supple outlines 

 characteristic of fishes, that the observer is some time 

 before he is assured they are not real fishes he is 

 looking at. Every scale, fin, and ray is in its place ; 

 and a brighter and more attractive set of natural 

 history objects it would be impossible to arrange. It 

 should be understood, however, that these are merely 

 casts, for which the fishes themselves have supplied 

 the moulds. We are not aware that Mr. Buckland, 

 or any one else, has ever published a description of 

 how these casts are prepared. Some time ago, when 

 desirous of learning the secret, we made all the 

 search we could, but failed to find anything beyond 

 an allusion. Since then we have experimented and 

 blundered until we have attained some degree of 

 success, and now have the pleasure of laying before 

 our readers the benefit of our experience. 



Let us observe that the student will find fish- 

 casting both a pleasant and profitable recreation 

 from sterner studies. It is artistic enough to require 

 the good taste of the most educated, and being as 

 cleanly as any cooking operation, there is no reason 

 why ladies should not engage in the work as well as 

 men. Moreover, it is cheap, and a little practice and 

 skill will soon enable any one. to take natural casts of 

 fishes, and to colour them well enough to be far 

 better natural history ornaments for halls and rooms 

 than the cases of stuffed birds we often see hung in 

 such places. 



The first thing is to get some well-ground plaster- 

 of- Paris. We have found that the second quality is 

 better for fish-casting than the first, as the latter sets 

 too quickly. The fish whose cast is intended to be 

 taken should be as fresh as possible. Fish stiffen 



