SCIENCE-GOSSIP. 



the galls he experimented upon are portrayed in 

 colour. The greater part of the volume is occupied 

 by a detailed account of his years of experiments 

 and observations on the oak-galls and their inmates. 

 The life cycle of each gall-fly is made up of two 

 generations, each one of which produces its own 

 sort of gall different from the other. One genera- 

 tion consists of two sexes, the other of one only. 

 The life of the gall-fly is generally very short, of 



days only, while the life of the insect inside the 

 gall may be months or years. These facts seem to 

 be common to all the gall-flies investigated. Many 

 of the life stories are more curious than the two 

 I have only touched upon as being perhaps the 

 best-known galls. There are the artichoke-galls, 

 the oak-apples, and the marble-galls; but your 

 readers will doubtless prefer to have the best part 

 of an interesting book to study for themselves. 

 Ambleside; June, 1895. 



AQUARIUM FOR MICROSCOPIC LIFE. 



By James Burton. 



T^VERYONE engaged to any extent in the study 

 ■^ of microscopical pond-life is aware how 

 interesting, and, indeed, almost indispensable, is 

 some kind of aquarium for watching the development 

 of, and having ready to hand, the various minuter 

 forms of animals and plants. In the "Notes of a 

 Home-Naturalist," which have appeared in the 

 new series of Science-Gossip, we see how fascin- 

 ating is this study, and also how well observation 

 may be carried on even with such simple apparatus 

 as a glass jam-bottle. Though vessels of this or 

 some similar kind answer the requirements of their 

 living inhabitants very well, having the advantage 

 of cheapness and being easily procurable, yet every- 

 one who has used them knows that it is practically 

 impossible to make satisfactory observation of the 

 more minute forms in them, owing to the distor- 

 tion caused by their shape and irregular surface. 

 The want of clearness of the glass also helps to 

 prevent the use of the ordinary pocket-lens, or 

 other means of magnification. 



On the other hand, an aquarium of the usual 

 type, but suitable size, with flat glass sides, must 

 either be bought, and that cannot always be 

 readily done, or made at home. Against these 

 drawbacks, however, must be placed the immense 

 advantage that a lens can be brought into action 

 on such a vessel, if requisite. Even, by some 

 special arrangements, the lower powers of the 

 compound microscope are available, and the con- 

 tained organisms may at all times be watched with 

 ease and pleasure. Anyone who has not tried this 

 form will be greatly surprised on their first ex- 

 perience of its clearness and general superiority, 

 while the endless amusement and profitable obser- 

 vation as well, are increased a hundred-fold. 



One of the greatest disadvantages of small 

 aquaria made in the usual way is their liability to 

 leak, but this tendency is quite overcome without 

 extra difficulty of construction in the form I pro- 

 pose to describe. I have two in use, home-made, 

 on this plan, which answer admirably. Of course 

 any size that suits the purpose or taste may be 



chosen, but for simplicity's sake I will describe one 

 which, when finished, is six inches long by six 

 inches high, and about two and a half inches 

 through from front to back, as this seems a very 

 convenient measurement. A strip of sheet zinc 

 should be obtained eighteen inches long and three 

 inches wide. Six inches from each end draw a line 

 across, which can be done with a sharp nail, three- 

 sixteenths of an inch from each side draw a line 

 from end to end. Where this line crosses the 

 others a small right-angled piece is to be cut out. 

 Now bend the edge of the sheet up to a right angle 

 along the lines drawn near the sides. This is best 

 done with a small hand vice or broad pair of pliers. 

 Next bend the strip where marked across, so that 

 the ends stand up at a right angle with the middle 

 portion, this will make the frame of the aquarium. 

 Two holes should be made in the middle portion 

 through which brass screws should pass into a 

 piece of board about seven and a half inches long, 

 by four inches wide, to form the stand. It is 

 better, if it can be done, to soft solder over the 

 heads of the screws and neighbouring parts of the 

 zinc bottom. The bottom corners of the frame 

 may also be soldered with advantage, and a strip 

 of zinc about half an inch wide across the top at 

 each side from end to end is also an improvement, 

 but may be dispensed with. In order to get the 

 glass the exact size, it is a good plan first to cut a 

 piece of cardboard to fit in the frame where it is to 

 go. Two pieces of glass about six inches by six 

 inches will be required for the front and back. 

 Put these in their places and then cut a piece to fit 

 closely at each end of the frame, within the ends of 

 the front and back pieces. Of course the glass in 

 this position cannot be seen through, because it 

 fits against the zinc ends, but it makes a very 

 strong joint, retains the other pieces in place, and 

 prevents all danger of leakage. When these ends 

 are fitted in, a piece should be cut to fit the 

 bottom ; this, when in position, will lie inside both 

 the front and back, and two ends, and will make a 

 sound joint there, where it is most important. 



