EXTERNAL ANATOMY OF INSECTS. 397 



tried ; and it will be quite impossible for myself, or any sys- 

 tematist, to explain away obvious relationships dependent on 

 essential similarity of structure, if indeed the grouping together 

 of intrinsically similar conformations be, as I suppose, the 

 basis of natural arrangement. 



Animals are formed on a number of perfectly distinct plans : 

 the organs which answer the purposes of perpetuating the 

 kind, of sustaining life, and of moving from place to place, are 

 present in all ; but the mode of their appearance affords those 

 characters which serve best to separate the kingdoms of animals 

 from each other. 



Many animals are merely an homogeneous jelly, inhabiting 

 the water, and adhering to earthy or vegetable substances, 

 or protected by an earthy tube secreted by their own bodies ; 

 of these, the history, i. e. the reproduction and mode of 

 existence, seems to foil inquiry, and to throw every impediment 

 in the way of those who would draw the line between the 

 animated and vegetable portions of the universe ; but, as we 

 rise in the scale of animated beings, we find they acquire the 

 power of locomotion, and either fly in the air, walk on the 

 earth, or swim in the water, moving at will from object to 

 object, as the great incentives to action, love and hunger, 

 destined wisely for the increase and sustenance of animal life, 

 may induce them. In these we find the body consists of two 

 principal portions besides the organs immediately connected 

 with the continuance of life : these portions are commonly 

 known as bone and muscle; the bone is solid, hard, and 

 capable of fracture, and serves for the attachment and support 

 of the muscular parts, which are softer, generally incapable of 

 fracture, and yield before the slightest pressure, by the motion 

 of their composite particles inter se. The disposition of bone 

 and muscle varies in the groups in which these parts are 

 distinct ; the bone is sometimes an articulated frame-work to 

 which the muscle adheres externally, clothing it as with a 

 garment; animals formed on this plan are called Vertebrata: 

 sometimes the bone is composed of little nodules, not arti- 

 culated with each other, but strung together like beads by 

 means of cartilaginous tendons ; these are termed Radiata : 

 sometimes the whole of the bone is united into one or two 

 large pieces, which are throughout the greater part of their 

 surface entirely unconnected with the animal, but constitute a 



