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 
% 




ise 
SSS SS SS 
ss 
Sa 


Ah 
ANUS 
ej 
I) 
Ih 
cs 


Fig. 16.—Hydrophilus in its four states. 
A, eggs; B, larva; C, pupa; D, imago, or perfect insect. 
observations 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 Elysées, at Paris, and on which the person who 
wishes to try his strength gives a strong blow with the fist, repre- 
sent a dynanometer of this kind. The one which Buffon had 
