MICROSCOPE IST-DOORS. 91 



scales assuming various forms. The scales stand in 

 exactly the same relation to the hairs in insects, 

 that the scales of fishes and reptiles do to the 

 feathers of birds and the hairs of mammals. Hair- 

 like scales are therefore not uncommon. At figures 

 229 and 230, such scales are represented, and may 

 be found on the common clothes-moth. 



The young microscopist, for whom our book is 

 written, and with which we hope to make him 

 dissatisfied, in order to facilitate his progress in 

 natural history inquiries, will not spend much time 

 in making dissections. Should he wish to do so, he 

 well find the structure of insects full of interest. 

 He has only to open a cockroach to see how 

 curiously their digestive apparatus is constructed. 

 This insect has a gizzard, and at the upper part it 

 is beset with six conical teeth, as seen at a, in 

 figure 220, plate 8 ; these teeth, working together, 

 reduce its food to a pultaceous mass previous to 

 digestion. When cut open, their position and re- 

 lations can be easily seen, as figured at b. The 

 gizzard of the cricket is also supplied with teeth, 

 seen at a, figure 221 ; it has three longitudinal 

 series of teeth, and each row in each series contains 

 seven teeth. The family of insects to which the 

 cricket belongs (Orihoptera) affords several other 

 instances of the same kind of structure in the 

 gizzard. It will be interesting to comp&re these 

 teeth of the insects with those of the mollusca and 

 the wheel animalcules. 



We must satisfy ourselves with having shown 

 the student the way to cultivate a large field of 

 interesting and instructive phenomena in the insect 

 world, without going further into detail. 



The tissues or textures of which animals are 

 built up or made may be easily procured in-doors. 

 We have spoken of the hard parts which form the 



