124 



SCIENCE-GOSSIP. 



Sound Organs in Cicadas. — Perhaps the most 

 interesting feature of the anatomy of the Cicada 

 and grasshoppers to the popular mind is the 

 musical apparatus by means of which they make 

 their peculiar note. This apparatus and the 

 sounds produced by it have been studied and de- 

 scribed by many naturalists. This gift of song is 

 found in the male insect only, and the true sound 

 apparatus consists of two small ear-like or shell- 

 like inflated drums situated on the sides of the 

 basal segment of the abdomen. These drums are 

 caused to vibrate by the action of powerful 

 muscles, and the sound is variously modified by 

 adjacent smaller discs, the so-called " mirrors," or 

 sounding-boards, and issues as the peculiar note 

 of the species, which if once heard is never likely 

 to be forgotten, or, if heard again, mistaken for 

 that of some other insect. The sounding-drum is 

 a tense, dry, crisp membrane, numerously ribbed 

 or plated, with the convex surface turned outward. 

 The ribs are chitinous thickenings or folds in the 

 surface of the parchment-like drum. The sound is 

 produced by the 

 rapid vibration of 

 these, set in motion 

 by two powerful mus- 

 cles situated within 

 the base of the abdo- 

 men. Fig. a gives a 

 view of the apparatus 

 from beneath, show- 

 ing the plates (light- 

 coloured) covering 

 the sounding discs ; 

 fig. b is a dorsal 

 view; fig. c is a 

 section at the base 

 of the abdomen, 

 showing attachment 

 of large muscles to 

 sounding-drum ; fig. 

 d is the sounding- 

 drum greatly en- 

 larged and in normal 

 position ; fig. e, the 

 same drawn forcibly 

 in by the action of 

 one of the muscles, 

 as in singing. 



Sound Organs of Cicad 



Difficulties of Amplification. — The beginner 

 in microscopy invariably wants to use his highest 

 objectives and shortest eyepieces first. It makes 

 no difference what the object is he wishes to 

 examine. He will put on a one-sixteenth or a one- 

 twentieth objective, and a half-inch solid eyepiece 

 to examine a beetle, if he has them, and if not, will 

 use the highest combination. He is very much 

 astonished and disgusted at the fact that he can see 

 nothing, and not infrequently imagines that he has 

 been cheated by the optician, and that his lenses 

 are worthless. He does not realize the fact that 

 the higher the amplification the smaller must be 

 the actual field of view, nor that the manipulation 

 of objectives and combinations increases in difficulty 

 with the increase of the amplification of which the 

 combinations are capable. Very few microscopists, 

 beginners and advanced students alike, understand 

 how to get the best work out of their lenses. The 

 manipulation of high powers is an art that requires 

 study and long practice ; the character of the light, 

 its direction, the position of the mirror and of the 

 condenser, the size of the aperture of the diaphragm, 

 all entering into the problem. 



Ants and Disease. — An epidemic in an ant 

 colony has been noticed by a Bombay bacteri- 

 ologist, who suspects the disease may be the 

 bubonic plague, and is experimenting to settle the 

 question. 



Crystals of Gold. — A very beautiful object 

 for the microscope may be obtained by the following 

 method. Make a ten per cent, aqueous solution of 

 neutral auric chl-oride (Au Cl 3 ), and of this put a 

 drop on a glass slip, spreading it with a glass rod. 

 Touch the drop with a piece of zinc plate cut to a 

 point, pushing the point well towards the centre. 

 The crystals will form in feathery masses. 



The Study of Fungi. — There are three 

 principal directions in which the study of fungi 

 may be pursued. Firstly, the larger fleshy fungi 

 only may occupy the attention, and these with the 

 object of ascertaining their merits or demerits as 

 articles of food. This is the purely gastronomic 

 interest, and its end is the production of pretty 

 pictures and the elaboration of savoury dishes. 



Secondly, the inves- 

 tigation may be an 

 absolutely scientific 

 one, upon purely 

 scientific lines, and 

 merely for systematic 

 purposes. Its great 

 objects are the 

 minute distinctions 

 between one species 

 and another, their 

 affinities and their 

 differences, the ela- 

 boration of schemes 

 of classification, and 

 the indefinite multi- 

 plication of names 

 and sections. This 

 is chiefly a mechan- 

 ical interest, and 

 its aim, the produc- 

 tion upon paper of 

 the most formidable 

 array of Latin names 

 in some novel se- 

 quence or combina- 

 tion. Thirdly, there 

 is the biological 

 method, in which the external form and develop- 

 ment is but one aspect, whilst names and affinities 

 are but helpers and not the objects of investigation. 

 In this process the whole of the life-history of the 

 parasite has to be ascertained as far as possible, all 

 its means of reproduction and whatever promotes 

 or hinders its career or affects its existence. This 

 last is evidently the only successful mode to be 

 adopted if the parasite is to be brought under 

 control, and if the investigator is to have a 

 thorough knowledge of its life and habits in 

 relation to its host-plant. 



Cleaning Cover-Glasses. — Braum recommends 

 the following process for cleaning cover-glasses. 

 Collect the cover-glasses to which cedar oil 

 adheres in a glass containing methylated alcohol. 

 Pour off the alcohol, wash with benzine, boil for 

 about half-an-hour with soda solution, stirring with 

 a platinum needle. When rinsing rub the glasses 

 with the hands to remove any adhering matter. 

 Then place them for twenty-four hours into acetic 

 acid and finally into ninety-six per cent, spirit. 

 Rub dry with a piece of soft leather and pass 

 through a flame. 



