!3 : 



HARDWICKE'S SCIENCE-GOSSIP. 



You will then have a very presentable and interest- 

 ing object. 



If the seeds are transparent enough to be viewed 

 by transmitted light without being mounted in 

 balsam, merely lay them on one of the glass slips, 

 cover them with thin glass and cement down with 

 the shellac as before. Finish off with coloured paper, 

 or if you have a turn-table, run a ring of white lead 

 varnish over the shellac ; when this is quite dry add 

 another : label and put away in your cabinet. 



Mounting in balsam is somewhat more difficult to 

 manage ; but practice makes perfect, and we must 

 not be disheartened by failure, but try again. The 

 great difficulty seems to be in laying the covering 

 glass down without the object shooting to the side, 

 or air bubbles making their appearance. However, 

 with a little care these difficulties will be overcome. 

 The seeds should be allowed to remain for some time 

 in turpentine previous to mounting. 



Whilst they are soaking, clean one of the glass slips, 

 and with one of the tubes transfer a drop of balsam 

 to the centre of it. Then take the seeds from the 

 turpentine and lay them in the drop of balsam on the 

 slide. Hold the slide for a minute over the flame of 

 the spirit-lamp until the balsam runs towards the edge, 

 taking care that you do not boil it or spill it. 



Have one of the covering slips ready ; lay it on the 

 balsam and lower very carefully. When you have it 

 down quite level, and seen that no air bubbles have 

 made their appearance, put it between the jaws of an 

 American clothes' peg filed flat down for the purpose, 

 and set it by to dry. I may here mention that it is 

 necessary to keep the slips in a warm place, or else 

 it will be weeks before the balsam is quite hard. 



After waiting until the balsam is quite hard set, 

 the slide may be cleaned with a rag dipped in spirits 

 of wine and finally labelled. 



The following are seeds easily obtained and worth 

 mounting as opaque objects : 



Anagallis, Anethum graveolens, Begonia, Carum 

 carui, Datura, Digitalis, Elatine, Erica, Gentiana, 

 Hyoscyamus, Hypericum, Linaria, Lychnis, Mesem- 

 bryanthemum, Nicotiana, Campanula, Petunia. 



The following as transparent objects in Canada 

 Balsam : 



Drosera, Hydrangea, Monotropa, Orchis, .Par- 

 nassia, Pyrola, Saxifraga. 



There are scores of others which are both beautiful 

 and interesting, and I trust that many will be in- 

 clined this summer to add most of these to their 

 cabinets. 



Devonport. Charles H. Dymond. 



Caterpillars and Onion-crops. — For several 

 years past the onion crops in this neighbourhood have 

 suffered severely from the ravages of the caterpillar of 

 some insect. Can any of your readers suggest a 

 remedy ? — P., Haslemere. 



NOTES ON HYDROPHILUS PICE US. 

 By James Fullagar. 



A CORRESPONDENT asks whether the Hydro- 

 philus piceus can be reared in captivity. It is 

 my opinion that it cannot, as I do not think that the 

 proper food of the larva is known. Perhaps the 

 following remarks, with the sketches, will help him in 

 obtaining the information he needs. On one very 

 bright sunny morning in March, 1872, while searching 

 for some subjects of natural history, I saw, basking in 

 the sun, on some weeds at the surface of a pond, a very 

 fine specimen of the female Hydrophilus, which I 

 soon, by the aid of my net, transferred to lry bottle. 

 As soon as I reached home, I placed her in a glass 

 vase, holding a gallon or more of water, in which 

 was growing a quantity of duckweed, and other pond 



Fig. 115. — Hydrophilus piceits, in the act of depositing her eggs. 



weeds. She went directly to the bottom and hid 

 herself under the weeds. I often noticed her as I 

 passed the vase, and on April 20, I observed that she 

 had a quantity of white matter at the posterior end of 

 her body, and I concluded, as she was at the surface 

 of the water, that she was either dying or dead, but 

 on examining her closely, I found that she was 

 spinning a silken nest, or cocoon, and depositing 

 therein her eggs. The nest was held firmly between 

 the hind legs, as shown in the sketch (fig. 115). After 

 the whole of the eggs were deposited, she covered them 

 up, rendering the top gradually smaller and smaller, 

 forming a sort of shaft, which, when the cocoon was 

 disengaged from between her legs, floated at the 

 top of the water, slightly attached to a piece of 

 anacharis, with the shaft, or tube, in an upright 

 position (fig. 116). When the cocoon was complete I 

 removed it to a smaller glass of clear water, so that 

 I could have a better view of the young when hatched. 

 This I watched from day to day until May 15, when 



