METHODS OF PROTECTION AMONG ANIMALS. 105 33 
contact with the rock, and the efficient covering given by 
the strong little shell to the soft-bodied animal within. 
The next class of animals is that of the fishes, lowest 
among chordate animals. for we need hardly in this short 
sketch consider the so-called semivertebrates, lancelets, sea- 
squirts, and sea-worms 
Below the true fishes is a class called Cyclostomata 
(lampreys or hag fishes), ealled also Marsipobranchii from 
their pouched sills, the hag fishes being not a little 
interesting as regards a singular form of protection they 
possess, viz., that of secreting enormous quantities of slimy 
mucus, which may even be 80 great as to interfere with 
fishing: i in their immediate neighbourhood. 
We have now to consider the various methods of 
protection among vertebrates, such as scales, spines, fur, hair, 
feathers, horns, poison-qlands, possessed by all below man, 
according to their individual needs. There are five order 
of fishes Rdecenbed: and a few only of these can be a 
upon by way of illustration. The means of protection 
among: fishes, generally speaking, consist of scales, teeth, and 
jins and jin-rays. Of scales there are three kinds, “ cfenoid” 
or comblike (as to their hinder edge), “ eyclotd”” or circular, 
and ‘ placoid” or plate-like, these last. being often composed 
of structures similar to those of the teeth, viz., dentine and 
enamel. The fin-rays are delicate bony rods supporting the 
fins. There is also as a rule in fishes a gill-cover or 
“ operculum” covering the gill-shts and gill-rays efficiently. 
The brains of fishes require protection to a great degree, and 
they obtain it in the delicately shaped and “carefully welded 
bones of the skull (e.g. in the skull of a perch there are 
thirty-seven pairs of bones enumerated), which as a rule has 
a pointed, tapering shape, with obvious advantage gee 
thereby in the rapid passage of the fish through the water 
shape advantageously imitated by man in the Scie se 
of his ships. The same advantage in its rapid movement is 
obtained by the beautiful imbr icated or overlapping arrange- 
ment of its scales with which we are familiar, and further 
assisted by the slimy abundant secretion of mucus. Lins 
ure among the earliest of organs among Vertebrates, in which 
the beautiful double purpose of protection (offensive and 
defensive) and direction by one organ is supplied. Not 
only does the fish progress "by means largely of its fins, but 
it at the same time steers and maintains its balanced 
position in the water with them, as is shown by thie 
