INTRODUCTION. 



23 



are said to undergo incomplete metamorphoses, the former com- 

 plete metamorphoses. Some never possess wings ; indeed, there 

 are others which undergo no metamorphosis, and are born pos- 

 sessed of 'all the organs with which it is necessary they should 

 be provided. 



Some curious researches have been lately made on the strength of 

 insects. M. Felix Plateau, of Brussels, has published some obser- 



Fig. 1 6. Hydrophilus in its four states. 

 A, eggs ; B, larva ; C, pupa; D, imago, or perfect insect. 



vations on this point, which we think of sufficient interest to 

 reproduce here. 



In order to measure the muscular strength of man, or of 

 animals, as the horse, for instance, many different dynamometric 

 apparatuses have been invented, composed of springs, or systems of 

 unequal levers. The Turks' heads which are seen at fairs, or in 

 the Champs Elysees, at Paris, and on which the person who 

 wishes to try his strength gives a strong blow with the fist, repre- 

 sent a dynamometer of this kind. The one which Buffon had 



