118 



HARDWICKE'S SCIEN CE- GOSSIP. 



" slack " of the thread accumulating below the tail. 

 If there is no projection of the edge of the branch 

 to throw it ofP, it scarcely ever fails to land upon 

 the branch and return the way it came. Erom the 

 perfect ease and regularity with which all these 

 slugs do this, I am inclined to think they are well 

 accustomed to it, as I noticed they almost always 

 did it if they did not find footing after descending 

 a few inclies ; and from the manner also that they 

 slipped off the end of the branch I am strongly of 

 opuiion that the whole process is involuntary. 

 When they get to the end of the branch, 1 never 

 saw one attempt to turn back, but it was while 

 protruding over the end, and feeling about for fresh 

 footing, that they slid off. The slug requires to be 

 in a particular condition. Gorged with food, tlie 

 slime is too thin, and the thread will not sustain 

 them ; but if kept over a night without food, they 

 are sure to perform well next morning if the con- 

 dition of the atmosphere is favourable— ?. e., warm 

 and moist. I do not believe the thread is used as 

 a means of voluntary descent, but that being fre- 

 quently subjected to the mishap of slipping off, 

 they have acquired the power of recovering them- 

 selves in this wav, which they do so systematically 

 as to leave no doubt about its being a voluntary 

 action, enabling them to avoid descending into 

 water, or anything injurious. I speak from nume- 

 rous experiments, but probably the autlior of 

 "Molluscan Threads" will be able to bring his 

 experience to bear upon the subject. I brought 

 this under the notice of the Dublin Natural History 

 Society'in 1S63-4 (vol. iv. part ii.).— William Harte, 

 F.R.G.S.I. 



Makine AQUARixm.— In reply to " J. G.," allow 

 me to give a few hints for the construction and 

 maintenance of a marine aquarium, gained from my 

 own experience. My first attempt was with an 

 ordinary propagating glass, 14-inch diameter, wiiich 

 I fixed in a stand. I first proceeded to put a layer 

 of clean sand, which I covered with shmgle, and pro- 

 cured some pebbles to which some seaweed was 

 growing, taking care to reject the thick olive-green 

 sorts, not only on account of their large size, but 

 because I knew that they make the water slimy. 

 Some of our common red seaweeds, finely branched, 

 I chose in preference, and some of the larger grass- 

 green seaweeds {Enteroworpha intestinal is), tufts of 

 scarlet hair-wort {Basya coccinea), and some few 

 other common red weeds. Care should be taken to 

 cleanse the weeds as much as possible without in- 

 juring them, before placing them in the vase, to 

 remove all decayed or impure matter that may be 

 attached to them, and so prevent, as far as possible, 

 the water from being poisoned. It is well to allow 

 the weed to remain a few days after planting before 

 the introduction of any animals. A little rockwork 

 is beneficial, for the enjoyment of the inhabitants of 

 the aquarium. It may be made of pumice-stone 

 cemented together with Portland cement. It should 

 be built to come above the surface of the water, in 

 order that such animals as the periwinkle, which 

 need air, should be able to enjoy it ; a few arch- 

 ways, nooks, and crannies should be made, among 

 which fishes might glide, and afford shelter for such 

 little creatures as do not court daylight or approve 

 of prying eyes. I now come to stocking, which is 

 perhaps the most difficult thing to do in London, 

 1 get my salt-water supplied me regularly from one 

 of the fishing-boats that come up the Thames 

 weekly to discharge their cargoes at Billingsgate, 

 and have it conveyed home by Parcels' Delivery. 



The men on tlie^e boats will gladly bring up with 

 them a stone jar or small cask of salt-water for a 

 mere trifle— in fact, I got my entire stock from 

 them, consisting of zoophytes, small fish, shrimps, 



I &c. Care must be taken not to introduce inmates 

 that are too large or too voracious, and thus over- 

 power the others. The most lively and amusing 



, inhabitants of the aquarium are the shrimps. They 

 are continually on the move, using their feet and 

 tails like paddles ; they soon become tame, and will 

 seize pieces of meat between their fore-legs, and 

 eagerly devour it. The prawn is still niore lively 

 than the shrimp ; but they must be small ones, or 

 they will make sad havoc by attacking and killing 

 other creatures. Among sea-anemones, none are 

 better fitted for the vase than the daisy-anemone 

 {Actinia bellis). Another beautiful kind is the 

 gemmed anemone {Actinia gemmacea), and one 

 which needs most care. Among the fishes suitable 

 for the vase >sthe common plaice {Plateasa vulgaris), 

 which, of course, must be very small. The stickle- 

 backs are rather too fond of fis^hting. A small sea- 

 urchin or two yEchinvs sphareu) will prove very 

 interesting, especially when its movements are ob- 

 served by the aid of a magnifying-glass.— JoA^ H. 

 Webb. 



Entomological Query.— The New Zealand 

 correspondent of the Times, writing under date of 

 January 10th, thus describes an insect which he 

 states is " new to science." " It is a black wasp- 

 like fly, but rather smaller than the English wasp. 

 Its habitat, or perhaps I should more correctly say, 

 its nursery, is a nest of clay built in some con- 

 venient crevice, and to the great annoyance of lady- 

 housekeepers, the upper folds of heavy window 

 curtains have apparently a peculiar charm for it. 

 Having selected a suitable spot for its operations, 

 it industriously carries tiny pellets of clay, which it 

 moistens and plasters over the curtain or crevice, 

 and on that foundation proceeds to erect a series of 

 separate clay cells, from five to eight in number, 

 the whole nest being from four inches to six inches 

 in length, and about the size and shape of a man's 

 little finger. The cells are not quite closed in, and 

 the little builder sallies forth on a spider-catching 

 expedition. Apparently the issue of the conflict is 

 never doubtful, for about half a dozen of various 

 size and kind are very speedily deposited captive 

 and comatose in each cell. In each cell, too, is 

 there laid a single t%^, the young grub from which 

 spends the days of his early infancy in consuming 

 the spiders which parental or maternal care has 

 provided for his sustenance, and which are un- 

 diminished in bulk and fulness a month or more 

 from the time of their capture." I should be glad 

 to know what insect is here described, or its pro- 

 bable genus. — C. Lovekin. 



Bats in Spring. —I find, on p. 93, in vol. for 1873, 

 a" note from a correspondent, H. B. E. Eox, under 

 the title of "Hybernation of Bats," wishing to know 

 whether it is a common occurrence for bats to fly at 

 midday in the spring of the year. I should like to 

 know also, as I saw one on the 14th April, near Ma- 

 ryhill (12 a.m.), flying about in the sunshine. I 

 watched it for about ten minutes, thinking it would 

 take to a hiding-place ; but it still continued to fly 

 over the same ground. — Alex. Macindoe. 



Old Trees and Squirrels. — In connection with 

 old trees, it may not be uninteresting to your read- 

 ers to know that on Saturday, Eeb. 7th, some men 



