51 



HARDWICKE'S SC1EN CE-GOS SI P. 



good ; but I have every reason to believe that Mr. 

 Beck had only arrived at half the truth ; for on 

 examining a web, I find that the concentric lines ruu 

 through the viscid drops, which appear like so many 

 beads strung on a thread ; this of course would not 

 be the case if a single viscid line ran by molecular 

 attraction into drops. Moreover, the thread itself is 

 dry, whilst the drops are viscid. 



I therefore infer that two pairs of spinnerets with 

 different kinds .of glands are employed simultane- 

 ously in forming the concentric lines ; viz., one of 

 the exterior pairs to make the thread, which is 

 varnished by a secretion from the inner pair, as it runs 

 out, and which secretion it is that runs into dots, just 

 as saliva will on a hair passed between the moistened 

 lips. There is plenty of work for the other pair of 

 exterior spinnerets in forming the radial lines, and 

 in swathing round the creature's prey, though pos- 

 sibly for this last operation the whole battery of 

 spinnerets may be used. I have spoken of the spin- 

 nerets as employed always in pairs ; but it seems to 

 me that this is doubtful, my own impression being 

 that one, as a general rule, is held in reserve, to be 

 employed when the other is exhausted, which I 

 know from observation is often the case. 



So much for the Epeira web, and now for Ciniflo 

 atrox. I have never had the pleasure of its acquaint- 

 ance; but hunting for if, after having read Mr. 

 Underbill's paper, I came across a web in a hole 

 of an oid elm-tree, which I fancied must be the web 

 of this species. On examination, however, under the 

 microscope, it evidently was not so ; and as I have in 

 vain tried to get a sight of the architect, I shall be 

 obliged to Mr. Underbill, or any one else, who will 

 tell me the name of the species. At all events, its 

 web is most curious and interesting ; it is not geome- 

 trical, and each thread is thickly furnished with 

 dots grouped together in grape-like bunches. No 

 single line could possibly fall into such groups by 

 molecular attraction, and I therefore consider it a 

 further proof of my theory, that two pairs of 

 spinnerets, with different glands, are employed simul- 

 taneously in forming the web. That the glands 

 become exhausted by constant use is evident, as I 

 have abstracted their web for the purpose of mount- 

 ing it each morning, and it has invariably been 

 renewed during the night; but on each successive 

 morning the characteristic conglomeration of dots 

 becomes smaller and fewer in number. 



CArT. Lang. 



ON PREPARING KLGM EOR THE 

 MICROSCOPE. 



TTITIIERTO my directions have been devoted 

 -"-"- exclusively to the process of mounting algae 

 on paper for the herbarium ; but 1 will now proceed 

 to describe my own method of preparing plants for the 

 microscopists, and especially for those persons whose 



business it is to mount specimens in Canada balsam 

 between circular glasses from 3^ in. to 2 in. diameter 

 (either for the gas lantern or gas microscope), and 

 for the ordinary 3 by 1 glasses for the table micro- 

 scope. I mention Canada balsam as the medium 

 for mounting algse as the best with which I am ac- 

 quainted for preserving the colour and structure of 

 the plants, and also for rendering them transparent. 



In the first place, I must observe, that with the 

 exception of the fuci, and some few of the coriaceous 

 and leathery-like red plants, I never put seaweeds 

 into fresh water, nor, when dried, into spirit of any 

 kind. In the first, they are apt to decompose or 

 change colour, and in the latter they generally lose 

 all their natural colour, which no amount of stain- 

 ing can satisfactorily restore. Colour can, of course, 

 be imparted to some of these marine plants, but not 

 the tint of their original endochrome. I have 

 mounted specimens of all the British fuci, but the 

 structure of most of them is so dense and stick-like 

 that it is almost impossible to get the balsam to 

 penetrate them sufficiently to obtain any amount of 

 transparency ; but with the exception of these coarse 

 rock weeds, I have mounted specimens of every 

 known British marine alga in Canada balsam, not 

 one of which has lost colour or suffered injury to its 

 structure in any perceptible degree ; and the pro- 

 cess by means of which I prepared them for the 

 balsam, I will now describe. 



Having obtaiued my specimens, either fresh from 

 the sea, or floated off paper on which they may have 

 previously been mounted, I immerse them, one at 

 a time, in clear, strained sea-water, and wash and 

 clean them well, until, with the aid of a lens, I can 

 discover neither dirt nor parasite on any portion of 

 either side of the plants. This is, with some of the 

 delicate red weeds, occasionally a troublesome ope. 

 ration, for several species of minute zoophytes adhere 

 very firmly to their fronds. However, by pressing 

 a finger of the left hand on the base of the specimen, 

 as it lies in the water, and holding it firmly in the 

 mounting dish, I scrape the zoophytes away with a 

 penknife, which must not be too sharp, and must be 

 applied very gently. As the calcareous particles 

 are detached from the plant, they float away in the 

 water, and an old worn tooth-brush may then be 

 employed to clear off loose bits of shell or sand, and 

 a final washing in clean water completes this por- 

 tion of the work. 



Some of the gelatinous species of green, olive, 

 and red seaweeds may be very satisfactorily mounted 

 on glass while they are floating in the water, espe- 

 cially when large specimens for the gas lantern are 

 required. When this is desired, say on a circle of 

 3a in., the glass should be washed clean, and then 

 slipped quickly under the floating weed. Then 

 gently raise the glass at one side until the base of 

 the plant is caught on its surface, and then, by 

 means of a smooth- pointed style of ivory, or a 



