474 



which surrounds the mouth and bears the tentacula, the name 

 of Lophophore was applied. 



The author gave the following account of the muscular 

 system : 



The muscles may be divided into eight sets. 

 1. The Retractor Muscles of the Alimentary Canal.- — These, 

 which are the largest and most powerful muscles of the animal, 

 consist of two fasciculi which arise from the lower part of the 

 sac, and thence pass upwards, one along each side of the ali- 

 mentary tract, to be inserted into the upper part and sides of 

 the pharynx. Their use is very obvious ; acting towards the 

 bottom of the fixed sac they retract the whole alimentary 

 canal, with the tentacular crown, so as to place them in a state 

 of security in the interior of the sac. 



2. The Rotatory Muscles of the Crown. — Thesealso consist 

 of two fasciculi which arise, along with the set just described, 

 from the lower portion of the sac, and passing up in company 

 with the retractors, separate from the latter at some distance 

 below the crown, and thence pass outwards to be inserted each 

 into the base of the arm of the lophophore of its own side. ^ 



Use, to rotate the tentacular crown, and depress the lobes. 



3. The Tentacular Muscles. — The muscular apparatus of 

 the tentacula consist of a set of delicate bands, which arise 

 from a peculiar structure which runs all round along the under 

 surface of the lophophore. These bands pass upwards, and 

 arriving at the interval between the roots of the tentacula, 

 each divides into two others which run along the opposed 

 sides of the tentacula. Use, to bend the tentacula to either 

 side. 



4. The Elevator Muscle of the Valve. — This is a small, but 

 very evident fasciculus, which, arising from that portion of the 

 lophophorewhich lies immediately behind the oral valve, passes 

 forwards to be inserted into the posterior surface of the latter. 

 Its use is to elevate the valve, and draw it backwards from the 

 mouth. 



