MUSCULAR SYSTEM. 13; 



animal. The peduncle and the mantle present distinct 

 musclar fibres, the dorsal part of the abdominal cavity near 

 the head, is attached by several muscular fasciculi to the 

 mantle and the shell, and a strong adductor muscle, as 

 in bivalves, passes straight across from one moveable piece 

 to the opposite. The fleshy parietes of the abdominal cavity, 

 the conical tubular funnel prolonged from that cavity, and 

 the haunches and innumerable tubular articulations of the 

 cirrhi present distinct muscular fasiculi. In the pedun- 

 culated forms, as in the pentalasmis, the whole of the con- 

 vex dorsal part of the enclosed animal, is covered with 

 crossing muscular fibres, which pass off in numerous sepa- 

 rate fasciculi to be attached to the inside of the proximal, 

 or closed part of the enveloping multivalve shell ; these 

 draw the animal forcibly and quickly back into the shell 

 after its body has been protruded for respiration or for 

 food. The haunches of the jointed members, and the base 

 of the funnel-shaped tube, also receive distinct muscles from 

 this fleshy dorsal part of the cirrhopod for their varied 

 movements. 



The annelides generally present a distinct muscular tunic 

 of a complicated structure immediately beneath the outer 

 tough and annulated integument, and intimately united 

 to it, besides the muscular fasciculi appropriated to the 

 motions of the lateral setae and cirrhi which extend from 

 muscular sheaths. This subcutaneous muscular tunic is 

 resolvable into distinct layers, and each of these into in- 

 numerable separate fasciculi ; the most exterior of which 

 have generally a transverse or an oblique direction, and 

 the most interior a longitudinal course, as seen in the 

 same part of the entozoa. These longitudinal muscles are 

 more or less "distinctly divided into longitudinal bands, as 

 those of the nematoid entozoa, and as we see even in 

 the holothuria, the actinia and many other of the radiated 

 animals. This muscular tunic of the annelides appears 

 to act on the interior viscera, as well as on the external 

 imperfectly developed segments. Its exterior layer is some- 

 times double, the one portion consisting of oblique fasciculi 

 and the other of tranverse, and both of these exterior 

 to the usual internal layer of longitudinal fasciculi. The 

 several muscles are disposed similarly in the different seg- 



