PHYLUM ECHINODERMATA 



403 



The coelome contains a fluid in which float numerous amcebo- 

 cytes, similar to those of the Starfish, and also a number of 



gen oft 



^ . raqi oss 



inter oss 



qen.du, 

 J me* 

 7naa. can 



int. ves 



FIG. 329. Internal organs of a Holothurian as seen when the body-wall is divided along 

 the middle of the dorsal surface. 6. 10. body-wall ; circ. mus. circular layer of muscle ; 

 cl. cloaca ; d. op. cloacal opening ; Cuv. orgr.jCuvieran organs ; gen. ap. genital aperture ; 

 gen. du. genital duct ; gen. gl. gonad ; int. Intestine ; inter, oss. inter-ambulacral ossi- 

 cles ; int. ves. intestinal haemal strands ; long. mus. longitudinal band of muscle ; mad. can. 

 madreporic canals ; mes. mesentery ; pol. ves. Poliau vesicles ; rod. amb. radial arnbulacral 

 vessel ; rod. oss. ambulacral ossicles ; ri. bl. ves. ring strand of hfemal system ; resp. respira- 

 tory trees ; ring-ves. ring-vessel of the ambulacral system ; stom. stomach. (After Leuckart.) 



flattened nucleated corpuscles containing a red colouring matter 

 haemoglobin almost identical with that which gives the red 

 colour to the blood of the higher animals. 



D D 2 



