July 1, 1865.] 



SCIENCE-GOSSIP. 



163 



MICEOSCOPY. 



Larva of a Gnat.— In the "Microscopic illus- 

 trations " by A. Pritchard is a description of a beau- 

 tiful transparent larva of a kind of gnat, wliich is to 

 be found in clear ponds at this time of year, and in 

 some places is very abundant. The drawings by 

 Mr. Pritchard are very nicely drawn, and give a 

 good idea of its appearance. But in addition to his 

 description I find it has two jaws, and feeds on 

 other animals— the blood-worm for one, as 1 found 

 the head and part of the body of one in its stomach. 

 Speaking of the stomach, there is a curious circum- 

 stance I have often noticed. On squeezing the larva 

 from its tail upwards, the stomach is forced, inverted, 

 out of its mouth, and then will be seen to be 

 covered with rows of spines, I suppose to retain its 

 food. The use of the shell-like bodies I cannot make 

 out; but they are pretty objects, and beautifully 

 spotted, bollow, and of a fibrous structure. The 

 larva casts its skin like others, but it requires close 

 looking to find it.— J?. T. Scott. 



Movements oe Endocheome in DiATOMACEiE.— 

 During an excursion with the members of the Tyne- 

 side Naturalists' Field Club, on Friday, May 26, 

 I made a collection of Diatomacese from the bed of 

 the river Blyth, a small river Avhich empties itself 

 into the sea near a town bearing the same name. 

 The stones on the bottom of the river were covered 

 with Pragilaria for an extent of some miles, and 

 intermixed with the Fragilaria there were many 

 beautiful varieties of Cymbella, Cocconema, Pleui'o- 

 sigma, Nitzschia, Gomphonenia, Surirella, &c. The 

 Cymbella lanceolatum or Cocconema gasfroides, I am 

 not quite certain which, they are exactly alike, and 

 the only mode of deciding the species is by seeing 

 the Cocconema on its stipes, Cymbella being a fice 

 form. I could not in the .gathering made observe 

 the least indication of stipes, and I therefore infer 

 that they are Cijmhella lanceolaiiim . In this I saw 

 what I bad never before seen, — a free motion of the 

 endochrome : it was as free as the motions of the 

 granules in the desired Closterium, but not quite so 

 regular. I examined the gathering three hours after 

 making tbe collection, and saw the motion of the 

 endochrome; — sixteen hom's after, and saw it yet 

 move freely, but only in one frustule ; — forty hours 

 after, and saw it very slightly in one frustule ; 

 niaety-eigbt hours after, but could not observe the 

 slightest motion in any frustules, although I exa- 

 mined many of them very carefully. I infer that the 

 best time for seeing the motions of endochrome 

 is when the diatoms are newly gathered. — T. P. B. 



Ho"W ABE Large Insects Mounted Whole? 

 — Though the text-books explain how to mount the 

 legs, antennae, or other separate parts of an insect, 

 they do not give the information necessary to enable 

 an amateur to mount an insect w^hole without air- 



bubbles. The great object to be achieved is to dis- 

 cover a chemical agent which will unite with the 

 balsam without injuring its clearness, and by which 

 to prepare the insect before placing it on the slide. 

 In the common process of mounting, the slide is 

 prepared, and the insect placed in the balsam, the 

 slide being then warmed, the clean thin glass is 

 allowed to drop gently on the specimen. But here 

 the great difficulty arises, for if tiie insect be a large 

 one, the body is too thick to allow the glass to lie 

 anything like flat, and even then the limbs generally 

 break off, to the utter destruction of the work. Mr. 

 Jabez Hogg's work on the microscope states that a 

 clergyman at Acton Abbotts has discovered a 

 medium which will attain the required object. The 

 slides sold at the opticians', and mounted on three- 

 inch circles (intended for the magic-lantern, though 

 equally adapted under the large objectives for the 

 microscope) are beautifully clear and perfect. How 

 is the process performed in these cases ? What is 

 the medium used? Perhaps some of your corre- 

 spondents may be able to solve this difficulty. Again : 

 How are young crabs and moderate-sized prawns 

 inounted tcJiole, — shell and all.'' I have seen some so 

 prepared at Newton's, Temple Bar, and as an 

 amateur I should, in common, no doubt, with many 

 others of your numerous correspondents, be glad to 

 attempt the use of the process.— .7. H. IF. 



Miceoscopig Powers.— The quarter-inch object- 

 glass of my microscope with the low eye-piece has a 

 field of view not larger than the aperture made by 

 an ordinary-sized sewing-needle. No. 5 ; yet, in that 

 field I have seen eleven circular diatoms from guano, 

 and these in no way crowded, but with spaces 

 between them. Each of these tiny circles possesses 

 markings, apertures, or elevations, of the most 

 minute yet regular character, hexagonal or circular. 

 I have endeavoured to count the number of aper- 

 tures in the radius of one of the smallest and coars- 

 est of these circles on my slide {Eudicta), and I made 

 up the number to be twenty-five. From this I 

 conclude that, at a rough calculation, there cannot 

 be less than three hundred apertures in the diameter 

 of one of the larger circles {Coscinodlsciis), eleven of 

 which, as I have said, scarcely fill a space equal to 

 the aperture of a sewing-needle. This, which any 

 amateur microscopist may verify for himself, with 

 perhaps more wonderful results, affords a practical 

 and ready method of explaining to many the reality 

 of the wonderful fact, that marvellous skill in design 

 and beauty in execution has been displayed on very 

 tiny atoms. And it shows the extraordinary per- 

 fection and power, even of a moderate-priced 

 modern achromatic microscope. No wonder that 

 the instrument has become popular, and that science 

 is the innocent and profitable subject of " Gossip" 

 indulged in by the " Lovers of Nature." — Lewis G. 

 Mills, LL.B., Armagh. 



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