280 MYEIAPODA. 



CHAPTER XI. 



MYEIAPODA*. 



(716.) THE Annelidans examined in the preceding chapter, with the 

 singular exception of the Earthworm, are only adapted to an aquatic 

 life : the soft integument which forms their external skeleton, and the 

 setiform and tentacular organs appended to the numerous segments of 

 their elongated bodies are far too feeble to support them in a less dense 

 and buoyant element ; so that when removed from their native waters 

 they are utterly helpless and impotent. Supposing, however, that, as a 

 mere matter of speculation, it was inquired by what means animals of 

 similar form could be rendered capable of assuming a terrestrial exist- 

 ence, so as to seek and obtain prey upon the surface of the earth, and 

 thus represent upon land the Annelidans of the ocean, a little reflection 

 would at once indicate the grosser changes required for the attainment 

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

 worms into an apparatus adapted to aerial respiration would be the 

 first requisite. The second would be to give greater density and firm- 

 ness to the tegumentary skeleton, to allow of more powerful and accu- 

 rately-applied muscular force by diminishing the number of segments 

 composing the annulose covering, and also, by converting the lateral 

 oars into jointed levers of support sufficiently strong to sustain the 

 weight of the whole body, to provide instruments of locomotion fitted 

 for progression upon the ground. Yet all these changes would be in- 

 efficient without corresponding modifications in the character of the 

 nervous system : the lengthened chain of small ganglia found in the 

 aquatic worms would be quite inadequate to wield muscles of strength 

 adapted to such altered circumstances ; the small encephalic brain would 

 be incompetent to correspond with more exalted senses ; so that, as a 

 necessary consequence of superior organization, the nervous centres must 

 be all increased in their proportionate development to adapt them to 

 higher functions. 



(717.) The changes which our supposition infers would be requisite 

 for the conversion of an aquatic Annelidan into a land animal are 

 precisely those which we encounter when we turn our attention from 

 the creatures described in the last chapter to the MYRIAPODA, upon the 

 consideration of which we are now entering : they form the transition 

 from the red-blooded worms to the class of Insects, and are intermediate 

 between the two in every point of their structure. 



* fivpia, ten thousand, i. e. many ; irovs, a foot. 



