ANIMAL LIFE AND THE MICROSCOPE 



amine it under the microscope, we shall see that 

 the apparent fibres are really very thin plates of 

 bone which wind and double upon themeselves in 

 a beautiful manner. The structure of these plates 

 gives strength to the bone without adding to its 

 weight. 



Snails are sure to attract the microscopist sooner 



or later, so too are slugs. Many of the latter have 



shells, small flat or ear-shaped shells, quite different 



to the portable homes of snails. In many young 



i snails, which may be killed by dropping into boiling 



■ water, we can find the shells so transparent that they 



form good objects for our microscope. Sometimes 



i they are composed of six-sided cells, sometimes of 



i beautiful star-shaped cells. 



From the microscopist 's point of view the most 



interesting feature of the snail is its rasping organ, 



I often wrongly termed the tongue. To find this 



organ it is necessary to open up the mouth of a 



dead snail, and if we seek the assistance of our lens 



while doing so, we shall have no difficulty in finding 



1 the rasp — it may be recognised by the minute teeth 



1 with which it is furnished. The whole structure 



t should be carefully removed and mounted upon a 



! slide. In some kinds of snails there are but a 



hundred teeth, other kinds, however, possess as 



i many as twenty-six thousand eight hundred. The 



; snail makes use of this remarkable organ to procure 



its food. Vegetation is pressed against a plate at 



i the top of the creature's mouth and literally filed 



into small pieces by the rasping organ. Captive 



123 



