HARD WICKE'S SCIENCE-GOSSIP 



259 



The Journal of Microscopy. — Besides the 

 paper on How Plants Grow, referred to in another 

 column, the October number of this journal contains 

 a paper by V. A. Latham, F.M.S., on Practical 

 Histology, being Part IV. of " The Microscope and 

 How to Use It ; " a second lecture on " Pond Life," 

 by Mr. W. E. Hoyle, M.A. ; "Half an Hour at the 

 Microscope with Mr. Tuffen West ; " Selected Notes 

 from the Society's Note-Books, &c. At the end are 

 six lithographic plates, which in this number are to a 

 large extent entomological. 



Testing Objectives.— In a note on this subject 

 in "The American Monthly Microscopical Journal," 

 the process of testing lenses by means of various 

 ■" test " objects is considered to smack somewhat of 

 charlatanism, though the use of a good Podura scale 

 is recommended. "The fact is, as every practical 

 observer well knows, the best test for a working 

 •objective is to use it in regular work for some time." 



Collins's "Special" Micro - Slides. — Mr. 

 Charles Collins's Catalogue of his " special" slides 

 for the present season is to hand, and with it half-a- 

 dozen sample slides, selected from different series, as 

 follows : From series No. 4 (Heads of Insects) the 

 head of the water boatman ; series No. 6 (the Silk- 

 worm and Moth of ditto), the trachea and spiracle (in 

 situ) of the caterpillar ; series No. 7 (Anatomy of 

 Blow-fly), the buzzing organ ; series No. 8 (Anatomy 

 of Honey-Bee), the wings, showing hooklets ; series 

 No. 9 (Anatomy of the Great Water-Beetle), the 

 trophi ; and from series No. 10 (Anatomy of the Oil- 

 Beetle), he sends the antennae. These slides ought 

 to be of great service to those who cannot provide the 

 objects for themselves. 



ZOOLOGY. 



Arion ater. — Besides the varieties of this slug 

 described in the June number, a few others have been 

 described as inhabiting foreign countries. One of 

 the most remarkable is var. Miilleri, black with a 

 pale greenish keel. Var. Draparnaudi of Moquin- 

 Tandon, dull red, with a yellowish or reddish foot- 

 fringe, is scarcely distinct from var. ritfa. I have 

 found it at Croydon, and 17 specimens of A. ater 

 collected at Bromley, Kent, were in the following 

 proportion : type 2, Jiigrescens 2, ncfa 10, and Dra- 

 parnaudi 3. Moquin-Tandon also mentions var. 

 rubra, red, and var. viresccns greenish with yellowish- 

 orange lateral bands. Not long ago I found at 

 Chislehurst two examples of the variety rtifa busily 

 •engaged in devouring the remains of a specimen of 

 Helix horlensis, var. lutea 12345, an d a Limax maximus 

 which had been accidentally crushed, thus affording 

 a good illustration of the carnivorous propensities of 

 this slug. Query, does it ever attack living snails or 

 slugs?— T. D. A. Cocker ell, Bedford Park, June 30. 



Mosquitoes killing Trout. — In a very in- 

 teresting letter which appears in "Science," in 

 advance of its publication by the U. S. Fish 

 Commission, Mr. C. H. Murray, of Denver, describes 

 how in 1882, when he was at the head-waters 

 of the Tumiche Creek in the Gunnison Valley, 

 Col., he watched for over half-an-hour the ways of 

 trout and mosquitoes. Very young trout kept coming 

 up to the surface of the water, possibly for more air, 

 so that the top of their head was on a level with the 

 surface. When this occurred, a mosquito, of which 

 a swarm was flying above, would alight upon the 

 trout's head, insert his proboscis into its brain and 

 suck away till he had extracted all the life juices, after 

 which he would fly away, and the dead trout turn on 

 his back and float down the stream. Mr. Murray 

 thinks that great numbers of trout, and perhaps other 

 infant fish in clear water, must come to their death in 

 this way. 



The Axolotl. — It appears that Miss Marie von 

 Chauvin, in continuing her researches on the develop- 

 ment of the Mexican Axolotl into the Amblystoma, 

 has succeeded in some instances in accelerating, 

 retarding, and reversing the metamorphosis, so that 

 the axolotl may be made to pass on into the con- 

 dition of a lung breathing animal, to remain for a time 

 in a state of suspended metamorphosis, or even to 

 revert to the axolotl stage once more. 



A swarm of Crabs. — A very interesting occurrence 

 has been reported from the island of Cuba, which 

 reminds one of the "showers of frogs" occasionally 

 heard of, namely the appearance of enormous quanti- 

 ties of small crabs. The keeper of a lighthouse at the 

 western end of the island says that they came in 

 floating patches of a reddish colour from a south-west 

 direction. They formed heaps upon the shore, which 

 they approached mostly during the night. They ap- 

 peared on four occasions last spring, "they invaded 

 the houses and the yards, and the tower of the light- 

 house up to a certain height, so that we had to brush 

 them away with brooms and shovels, and finally to 

 close the doors and windows, and cover the openings 

 of the water-tanks with canvas and sacking;." 



The Sun-fish.— It appears that the sun-fish which 

 has comparatively imall pectoral fins, uses them 

 only as balancers in swimming, and progresses almost 

 exclusively by means of the dorsal and anal fins 

 which are large, about the same size, and placed in 

 the same vertical line. In a letter to " Science " by 

 Mr. John A. Ryder, it is said that the fish moves 

 the dorsal and anal fins synchronously from side to 

 side, twisting them at the beginning of each stroke 

 into the form of a screw propeller blade ; the great 

 expanse of the body gives the fish stability. Its 

 slightly developed tail it uses as a rudder, by which, 

 however, it cannot turn very quickly. 



