56 



POLYPIFERA. 



thickened lining membrane of the cell. This 

 cavity once formed, the development of the 

 different organs proceeds rapidly. First, in 

 the middle of the cavity there appears a longi- 

 tudinal fold resembling two lips (fig. 62. 2), 

 which, as they approach each other, divide 

 the cavity of the body into an anterior and a 

 posterior compartment. The two lips, which 



have a valvular appearance, become indented 

 very regularly along their margins, and are 

 soon recognisable as the rudiments of the 

 tentacular circle (Jig. 62 3). 



At this epoch, it must be remarked, the 

 polype presents two cavities distinct from 

 each other. There is a space between the 

 walls of the body and the parietes of the 



Fig. 61. 



Laguncvla repens, magnified 400 diameters. 



A. The animal completely retracted into its cell ; 

 B, another individual completely expanded ; C, the 

 outlines of another individual retracted. The same 

 letters apply to each of the figures. The various 

 viscera are situated in different planes, but are here 

 represented all in the same. 



a, the tentacles, protruded and expanded in B. ; 

 the arrow indicates the set of the currents caused 

 by the vibration of the cilia; I, buccal cavity; c, 

 valve separating this cavity from the oesophagus; 

 d, oesophagus ; /, pyloric valve ; g, cilia, producing 

 the rotation of the food in the stomach ; h, thickness 



of the parietes of the stomach ; i, intestine ; k, ex- 

 crement contained in its interior ; Z, anus ; m, testicle ; 

 n, ovary ; o, ovum escaped from the ovary ; p, aper- 

 tures through which the eggs are expelled, with an 

 ovum in the act of escaping , q, spermatozoa, freed 

 from the testicle, and floating in the fluid that sur- 

 rounds the digestive canal ; r, s, t, u, v, muscles, re- 

 tractors of the parts to which they are attached ; tc, 

 principal retractor muscle ; .r, transverse folds of the 

 collar ; y, bands, perhaps muscular, of the collar ; , 

 nervous oesophageal ganglion ; p, stalk 5 y, a young 

 bud. (After Van Beneden.) 



