138 MUSCULAR SYSTEM. 



ments of the same: worm, and even in different worms, 

 in the larvae of insects, in myriapods, and in the segments 

 of the trunk of most of the articulated classes of animals. 

 In the common earth-worm, as in many others, the mus- 

 cular sheaths for the extention and retraction of the short 

 conical curved and pointed feet consist chiefly of radiating 

 fibres which extend from around the base of these hollow 

 spines. The fleshy lips of this animal are provided with 

 several longitudinal and circular muscles appropriated to 

 their varied movements, and the anus is distinctly furnished 

 with levator and spincter muscles. 



From the aerial respiration and the higher general de- 

 velopment of most of the entomoid articulata their mus- 

 cular fibres are more dense and irritable, and from the 

 greater consolidation and distinctness of their segments, 

 their muscular fasciculi are more isolated and more me- 

 thodically disposed, than in the softer trunks of the aquatic 

 helminthoid tribes. The myriapods, like the worms, having 

 their segments and their lateral appendices equally developed 

 from the one extremity of the trunk to the other, without 

 distinction of thorax and abdomen, present the greatest 

 similarity in the muscular system throughout all their seg- 

 ments, and the greatest resemblance to the disposition of 

 that system in annelides and in the larvae of insects. More 

 than four thousand distinct muscles are found in the larva of 

 the common cossus ligniperda, and these are disposed in con- 

 centric strata, the fasciculi of which are directed, some longi- 

 tudinally some transversely, and others with various degrees 

 of obliquity, passing, as in the trunk of most adult entomoid 

 animals, from the concave inner surface of one segment, to 

 the anterior enclosed margin of the next succeeding. As the 

 extremities and wings for progressive motion become deve- 

 loped from the thorax, the muscular apparatus of that por- 

 tion of the trunk becomes more developed than in any other 

 segments. In the annexed figure from Straus, representing 

 the principal muscles of the trunk of the male cock-chaffer, 

 melolontha vulgaris (Fig. 6*4,) we observe that the interior 

 layer of muscles of the segments of the abdomen (/,) run in 

 a longitudinal direction, like those of the helminthoid 

 classes. The muscles of the abdominal segments consist 

 generally of parallel short fasciculi, which retain the same 



