CHYLAQUEOTJS FLUID. 



477 



(1250.) The aliments,before admission into the stomach, accumulate in 

 a cavity formed at the commencement of the digestive tube (fig. 242,/), 

 which in most genera is defended by a largely developed lip (d) that 

 opens and shuts like a valve ; this lip is densely covered with cilia, the 

 action of which is very energetic. 



(1251.) The anus (j) is always situated at the base of the tentacular 



zone. 



(1252.) The food of the fluviatile Polyzoa consists of Infusorial 

 animalcules and the microscopic Desmidieae which abound in the waters 

 they frequent, and whose remains Fig. 242. 



are distinguishable both in their 

 stomachs and in the contents of the 

 intestine. They are likewise easily 

 made to swallow carmine, sepia, and 

 other colouring substances. 



(1253.) There seems to be no 

 doubt relative to the nature of the 

 circulation in these animals. The 

 place of blood seems to be altogether 

 supplied by the chylaqueous fluid. 

 This fluid is not contained in vessels, 

 unless the cavities of the tubular 

 tentacula be considered as such, but 

 moves freely in all directions around 

 the parietes of the digestive canal. 

 There is consequently neither heart 

 nor any vascular system, the chyl- 

 aqueous fluid, which thus repre- 

 sents the blood, being kept in con- 

 tinual movement in the periintes- 

 tinal cavity by the action of the 

 cilia that cover the exterior of the 

 intestinal apparatus. It is therefore ciliary action that determines 

 the course of the aliment in the interior of the alimentary apparatus, 

 and of the fluid external to its walls the cilia thus answering the pur- 

 pose of a heart as well as of the muscular coat of the intestines. 



(1254.) All the viscera of the body being thus bathed by the chyl- 

 aqueous fluid that surrounds the intestinal canal, they receive directly, 

 through the intermedium of that fluid, both the materials for nourish- 

 ment and the means of respiration. 



(1255.) Reproduction among the freshwater Polyzoa is accomplished 

 in two ways by gemmation and by true ova. The first of these modes 

 resembles exactly what has been described as existing among the marine 

 genera; but as regards the process of oviparous reproduction, there 

 are some remarkable points of difference that require notice. 



Fredericella sultana, : d, mouth ; f, pharynx ; 

 .;', anal orifice. 



