Oct. 1, 1367.] 



HARDWICKE'S SCIENCE-GOSSIP. 



225 



which I take to be alimentary matter; it freely 

 floats out with the ova when an incision is made, or 

 it may be obtained directly from a cut portion by 



Fig. 224. Bi-caudate Ovum, x 575. 



pressure. Examined under a 1-inch objective,' it 

 is seen to consist of semi-transparent granules or 

 corpuscles ; and it appeared of some importance to 

 endeavour to ascertain what they consisted of — not 

 merely from curiosity as to the worm's diet, but as 

 tending to show whether or not they might be 

 regarded as injurious to the vegetable produce of 

 those gardens where they exist in sucb numbers. 

 The result of sundry experiments seems, however, 

 clearly to show that this granulated matter is 

 neither of animal nor vegetable composition, inas- 

 much as it remained unchanged by the action of 

 Schultze's test and of iodine. By adding sulphuric 

 acid to a portion already treated with iodine, very 

 minute isolated patches only gave a purple re- 

 action, seeming to indicate the presence of cellu- 

 lose; but strong sulphuric acid acted powerfully 

 upon it, disengaging small bubbles of gas. Finding 

 this to be the case, I allowed it to stand aside for a 

 couple of days ; and at the end of that time I found 

 floating in the liquid numerous bundles of the well- 

 known acicular crystals of sulphate of lime. Eor 

 preservation as microscopic objects, entire speci- 

 mens of Mermis may be readily mounted, freely 

 floating in cells filled with water or glycerine. 

 When intended to be viewed as transparent objects, 

 they should be thoroughly saturated with water, 

 then placed in the required position between two 

 glass slides, and allowed to dry under pressure, 

 after which they can be mounted in the usual 

 manner in glycerine jelly or pure glycerine, under a 

 glass cover only. With the ova alone greater care 

 is necessary ; and to avoid the results of pressure 

 they should be protected by a very shallow cell, in 

 which glycerine is undoubtedly the best medium for 

 their preservation. All my attempts with balsam 

 have turned out badly ; for though free from 

 bubbles, the sacs have in every case been broken, 

 and the escape of the contained fluid has caused a 

 blurred appearance round all those of the ova which 

 were not completely isolated. 



THE DRAGON-FLY. 

 By A. S. Packard, Jr., M.D. 



WERE we to select from among the insects a 

 type of all that is savage, relentless, and 

 bloodthirsty, the Dragon-fly would be our choice. 

 From the moment of its birth until its death, 

 usually a twelvemonth, it riots in bloodshed and 

 carnage. Living beneath the waters perhaps eleven 

 months of its life, in the larva and pupa states, it 

 is literally a walking pitfall for luckless aquatic 

 insects ; but when transformed into a fly, ever on 

 the wing in pursuit of its prey, it throws off all 

 concealment, and reveals the more unblushingly its 

 rapacious character. 



Not only does its horrid visage and ferocious 

 bearing frighten children, who call it the " Devil's 

 Darning-needle," but it even distresses older per- 

 sons, so that its name has become a byword. Could 

 we understand the language of insects, what tales 

 of horror would be revealed ! What traditions, 

 sagas, fables, and myths must adorn the annals of 

 animal life regarding this Dragon among insects ! 



To man, however, aside from its bad name and 

 its repulsive aspect, which its gay trappings do 

 not conceal, its whole life is beneficent. It is a 

 scavenger, being like that class ugly and repulsive, 

 and holding literally, among insects, the lowest rank 

 in society. In the water, it preys upon young mos- 

 quitoes and the larvse of other noxious insects. It 

 thus aids in maintaining the balance of life, and 

 cleanses the swamps of miasmata, thus purifying 

 the air we breathe. During its existence of three 

 or four weeks above the waters, its whole life is a 

 continued good to man. It hawks over pools and 

 fields and through gardens, decimating swarms of 

 mosquitoes, flies, gnats, and other baneful insects. 

 It is a true Malthas 5 delight, and, following that 

 sanguinary philosopher, we may believe that our 

 Dragon-fly is an entomological Tamerlane or Napo- 

 leon sent into the world by a kind Providence to 

 prevent too close a jostling among the myriads of 

 insect life. 



We will, then, conquer our repugnance to its 

 ugly looks and savage mien, and contemplate the 

 hideous monstrosity, — as it is useless to deny that 

 it combines the graces of the Hunchback of Notre 

 Dame and Dickens's Quilp with certain features of 

 its own, — for the good it does in Nature. 



Even among insects, a class replete with forms 

 the very incarnation of ugliness and the perfection 

 of all that is hideous in nature, our Dragon-fly is 

 most conspicuous. Look at its enormous head, 

 with its beetling brows, retreating face, and heavy 

 under jaws, — all eyes and teeth, — and hung so loosely 

 on its short, weak neck, sunk beneath its enormous 

 hunchback, — for it is wofully round-shouldered, — 

 while its long thin legs, shrunken as if from disease, 



