86 THE MICROSCOPICAL NEWS. 
carapace of another animal, so as to get at its soft parts for food. 
The variety and great beauty of these structures can only be ap- 
preciated by careful investigation under the microscope. The 
odontophores are probably chitinous in substance, although we 
might easily imagine them to be composed of true dentine, which 
they so much resemble. 
From odontophores to the teeth of fishes is a long jump, but 
we still find the teeth of most fishes retain the same prehensile 
characteristics. In fishes we begin to discover distinct dental 
structures formed around the maxillary arches. It is true that in 
the lowest forms—such as the glutinous hag, and kindred species— 
the dental system is represented by only a single tooth; but as. 
we progress upwards we find an almost endless variety of dental 
structures. So that, as Dr. Richard Owen says, ‘In form, sub- 
stance, situation, and mode of attachment fishes offer more striking 
modifications than do those of any other class of animals; and 
the anatomist finds a difficulty in obtaining a command of language 
sufficiently varied to portray the singular diversity and beauty, and. 
the interesting physiological relations, which are manifested in that 
part of their organization.” But while there is such a variety in 
the teeth of fishes, a great many of them are in shape simple cones. 
The office of these cones is almost wholly prehensile, and they 
answer the purpose required so long as the animal lives on food 
that is swallowed whole. But when the food has to be divided into. 
pieces, new forms of teeth are developed. First, we find the cones 
attaining great size, as in the canines of the carnivora, for the pur- 
pose of seizing the prey and tearing the flesh ; and moreover these 
tusks eventually become weapons of attack and defence. The use 
of these teeth is apparent even in the less prominent but more 
complicated canines or eye-teeth of man, for we yet see the less 
refined classes gnaw a bone by holding it in the fingers instead of 
scraping it withaknife. Next we find the cones coalescing, so as to 
form the “sectorial” or scissor-like teeth of the carnivora. These 
teeth seem to be formed expressly for the division of the flesh. 
Then we find another combination of cones, to form what Dr. Owen 
calls the “tubercular molars,” which are used to crack the bones 
to get at the marrow, as seen in the dog, hyzena, &c. ‘The coales- 
cence of the simple cones to form the teeth of the carnivorous and 
omnivorous animals must first commence in the union of two or 
more of the germs from which the teeth arise, although we are as 
yet unable to fully demonstrate this proposition. For we find the 
crowns of these teeth made up of a number of cones fused into 
one, over which the enamel has flowed, following the elevations 
and depressions caused by the points of the cones projecting be- 
yond the general mass; and then, when the crown has formed, we 
find the fused tooth germ again partially separating to form the 
