'580 ORGANS OF SECRETION. 



animals, and the larger ramified cceca the liver. There are 

 numerous distinct matters eliminated from the food by the 

 vital processes of echinoderma, but very few developed 

 glandular organs appropriated to their formation; the 

 various colouring materials of the surface, of vivid hues, 

 both in the naked and the testaceous forms ; the numerous 

 calcareous deposits of granules, spines, and shells ; the co- 

 pious solvent secretions of their digestive cavities, and the 

 mucous secretions poured out on the surface of holothurw, 

 and other naked species ; the supposed calcifiant gland of the 

 stellerida, which is a small vascular sac filled with a thick 

 grumous secretion, consisting chiefly of minute calcareous 

 crystals ; and the numerous distinct sacs or tubuli, for the 

 periodical development of ova. The internal branchiae of 

 holothurue have the form of long hollow ramified tubuli, and 

 into their wide ducts, close to the cloaca, open several small 

 isolated follicles, like a rudimentary kidney or renal tubuli ; 

 small isolated salivary follicles are observed also in some of 

 the species, opening into the cavity of the mouth. 



THIRD SECTION. 



Secreting Organs of the Diploneurose or Articulated Classes. 



The glandular organs of articulata are more distinct, more 

 numerous, and more constant than in the radiated classes, 

 but they still manifest the simplest follicular character, both 

 in the ordinary chylopoietic, and in the newer and peculiar 

 glands, and this simple condition of their chylopoietic glands 

 accords with the nutritive character of the food in most of 

 these parasitic or carnivorous tribes. The liver is rarely 

 imperceptible in the entozoa, and has been long since shown 

 by Rudolphi, Bojanus, and others ; and salivary glands have 

 also long been observed in the animals of this class, as in 

 the trematode diplozoon, described by Nordmann, and in the 

 pentastoma, by Cuvier. In most of the trematode and 

 lowest forms of parenchymatous entozoa, as in many echi- 

 noderma and annelides, the liver consists of numerous 

 ramified coeca prolonged from the sides of the digestive 

 canal ; and in the higher nematoid species, the biliary tubuli 

 are restricted to small short follicles surrounding the long 



