140 HOLOTHURICE. 



made on the living animal, the respiratory movements 

 in Holothurice. Suppose the animal desires to take 

 in a quantity of water, it first contracts the anterior 

 end of its body, and then forces all the water it may 

 contain into the posterior end, which now bulges out- 

 wards. A fixed point for the action of the numerous 

 small muscles which pass between the outer surface of 

 the cloaca and inner surface of the fleshy envelope of 

 the animal is thus provided ; these muscles then con- 

 tract and distend the cloaca. The sphincter fibres sur- 

 rounding the anus then relax, and the sea- water rushing 

 through the opening completely fills the cloaca. Then 

 the anus firmly closes, and at the same time the aper- 

 ture of the intestinal canal is shut. The muscular wall 

 of the cloaca then contracts, and presses the water into 

 the respiratory tree through the aperture at each side 

 of the terminal part of the intestinal canal. The ani- 

 mal respires, when active, four or five times in a minute. 

 He described also the existence in Holothurice of a 

 twisted calcareous tube close to the tube which con- 

 veys away the secretion of the genital organs ; this he 

 regarded as homologous with, the jointed tube which, 

 in the star-fishes, connects the madreporiform tubercle 

 with the water-ring. 



Distoma. — In his account of the anatomy of Dis- 

 toma hepatica, he considered, contrary to the opinion 

 generally held by anatomists, that it contained a cavity 

 in its interior like the cavity of the Holotliuriadce, in 

 which the viscera of distoma were situated. 



He gave a careful description of that curious para- 



