7 6 



Invertebrata. 



cated worm . 

 A, Pharynx, or re^pira 

 tory 

 body ; 



masses of semi-transparent, often 

 gristly material, and of a whitish, 

 pink, or brownish colour. They 

 vary in length from i to 6 inches. 



In each tunicary there are two 

 apertures on the surface; one of these 

 (c, fig. 46) opens into a large chamber 

 whose wall (e) is a vascular mem- 

 brane, and at the bottom of which 

 is the mouth (k). The digestive canal 

 ends at the bottom of a second 

 chamber (/"), of which the lower or 

 hinder opening is the outlet. Be- 

 tween these two chambers, which 

 thus lie over the digestive canal, 

 there is a partition wall which is 

 pierced by many small holes whereby 

 the water which enters into one can 

 pass into the other, thus bathing the 

 surface of the lining membrane, and 

 enabling the blood contained in the 

 spaces in its texture to become 

 aerated. The first chamber (fig. 46) 

 is called the branchial chamber, the 

 second is called the atrial. 



Between the opening of the 

 branchial chamber and the atrial ori- 

 fice there is a nerve ganglion send- 

 a tuni- m g a fi ne 1P of branches around 

 the mouth. The heart lies at the 



ocy Bstmac c 



egg-producing organ! it the vessels pass into the wall of 



