144 ACTINOZOA. 



face the flattened sides of the mouth. The acces- 

 sory actinomeres, slightly narrower than either of 

 the preceding, serve to occupy the four inter- 

 spaces which occur between the lateral and an- 

 tero-posterior pairs. 



The lateral actinomeres are further distinguished 

 by the presence in each of a large sac, which opens 

 obliquety, outwards and downwards, about mid- 

 way between the equatorial region and the apical 

 pole of the body. From this sac the animal has 

 the power of protruding at pleasure a long, highly 

 contractile, beautifully fringed, tentacle. 



Immediately within the apical pole is situate a 

 peculiar body, supposed to be an organ of sense, 

 which is best termed the ' ctenocyst.' Upon this 

 rests a nervous mass from which issue small fila- 

 ments. The structure of these parts, as also of 

 the prehensile, locomotive, and reproductive appa- 

 ratuses are described in their appropriate para- 

 graphs. At present let us chiefly notice, in con- 

 nection with the form of the bod}^, the arrange- 

 ment of its somewhat complex nutrient system. 



(A^- 27.) 



This system may be said to commence in the 

 stomach, or digestive sac, a cavity having the 

 general form of an elliptic cylinder, and extending 

 from the mouth through the longitudinal axis 

 of the body, for about '6 of its entire length. 

 Slightly contracting below, the digestive sac is 

 seen to open into a much wider and shorter cavity, 

 also axial in its direction, known as the ' funnel,' 

 which gradually diminishes in diameter as it ap- 

 proaches the apical pole of the body, to terminate 

 just above the ctenocyst and nervous mass. From 

 the funnel three pairs of canals are given off. 



