HTDROZOA. 3 J 



a while in this position, the fundus of the gastric 

 chamber contracts, and forces the globule through 

 the valve, which appears to dilate at the same 

 moment." 



The walls of the peduncle are thin and muscular. 

 Those of the gastric chamber are comparatively 

 thick, while its cavity is wider than any other 

 part of the interior of the polypite. In addition 

 to the cilia, which clothe its endoderm, the surface 

 of this layer is often elevated into a number of 

 villi, or conical processes, which in Physalia attain 

 a length of '01 of an inch. Such villi, or ridge- 

 like enlargements which arise in their stead, have 

 been observed within the polypites of many Hy- 

 drozoa {fig. 5, 6). The coloured contents, occa- 

 sionally noticed in these, and similar elevations, 

 are regarded by some anatomists as the most 

 rudimentary form of hepatic apparatus. In Ve- 

 lella and Porpita, more certain indications of a 

 liver are presented by a dark brownish mass, which 

 arises in connection with the digestive cavity of 

 the large central polypite (fig. 21, a). 



The nutrient matters elaborated within the 

 bodies of the polypites are finally transmitted to 

 the somatic cavity {fig. 5, b). Plere they undergo 

 an imperfect sort of circulation, a phenomenon 

 the occurrence of which has been more especially 

 observed within the long cosnosarc of Tubular ia 

 indivisa. Currents have been seen to course up 

 and down the long stem of this Hydrozoon which 

 occasionally appear to flow through distinct tubes, 

 but these are nothing more than irregular cavities 

 produced by vacuolation of the endoderm {fig. 

 16, c, d, and e). A circulation of albuminous 

 particles also takes place within the peculiar 



