MYRIAPODA. 73 



an aquatic life. The soft integument which forms their outer 

 framework, and the feeble organs appended to the numerous 

 segments of their lengthy bodies, are far too weak to support 

 their weight in a less dense and buoyant element, so that, when 

 removed from their native waters, they are utterly helpless and 

 impotent. Supposing, as a matter of mere speculation, it was 

 inquired, by what means animals so constructed could be ren- 

 dered capable of assuming a terrestrial existence, so as to seek 

 and obtain their food upon the surface of the earth, and thus re- 

 present upon land the Annelidans of the ocean ; a little reflection 

 would at once indicate the grosser changes required for the attain- 

 ment of such an object. To convert the water-breathing organs 

 of the aquatic worms into an apparatus adapted to breathe the 

 air would be the first requisite. The second would be to give 

 greater firmness to the tegumentary skeleton, to allow of more 

 powerful and accurately applied muscular force, by diminishing 

 the number of the segments, and by converting the lateral oars 

 into jointed limbs sufficiently strong to sustain the whole weight 

 of the body, to provide instruments of locomotion fitted for pro- 

 gression upon the ground. Yet all these changes would be 

 inefficient without corresponding modifications in the nervous 

 system. The lengthened chain of minute ganglia, met with in the 

 leech (Fig. 57), would be quite inadequate to wield muscles of 

 strength adapted to such altered circumstances ; the small brain 

 would be incompetent to correspond with more exalted senses ; 

 so that, as a necessary consequence of superior organization, the 

 nervous centres must all be increased in their proportionate 

 development, to adapt them to higher functions. The changes 

 which our supposition infers would be requisite for the conver- 

 sion of an aquatic Annelid into a Myriapod are precisely those 

 which we encounter. The air-breathing animals which we have 

 now to describe form the transition from the red-blooded worms 

 to the class of insects, and are intermediate between these two 

 great classes in every part of their structure. The body of a 

 Myriapod consists of a consecutive series of segments of equal 

 dimensions, but, unlike those of the Annelidans, composed of a 

 dense, semi-calcareous, or else of a firm, horny substance, and to 

 every segment is appended one or two pairs of articulated legs, 

 generally terminated by simple points. 



The anterior segment, or head, besides the organs belonging to 

 the mouth, contains the instruments of sense, consisting of simple 

 or compound eyes, and of two long and jointed organs, called 



