472 



RECENT BRACHIOPODA 



ing of these cilia in Argiopc (Cistella) when the animal is well 

 fed, and their elongation when the animal is hungry. Amongst 

 the ciliated cells certain glandular cells have been described. The 

 so-called liver consists of two more or less branching aiands, 

 which open by wide apertures, one on each side of the stomach. 

 It seems probable that a good deal of digestion is carried on in 

 these glands, since the diatoms and other minute organisms 

 upon which the Brachiopoda live are usually found in the 

 branches of these glands, and the glandular cells lining the 

 tubules vary much in appearance according to the animal's state 

 of nutrition. 



The Body Cavity 



The alimentary canal and liver occupy a considerable portion 

 of the body cavity or general space of 

 the l)ody ; this space is to some extent 

 cut up by the various mesenteries 

 above mentioned. It also lodges the 

 reproductive organs and the excretory 

 ducts. Its walls are ciliated, and the 

 action of the cilia keeps in motion 

 the corpusculated fluid that bathes the 

 various organs in the Ijody cavity. Tlie 

 mantles, which are nothing but flat- 

 tened leaf-like extensions of the body 

 wall lining the shell, also contain 

 diverticula of the l)ody cavity, wdiich 

 may he simple flattened spaces or may 

 be broken up into definite channels, as 

 in Lingtda (Fig. 315). It seems not 

 improl)able tliat the body cavity fluid 

 is aerated through the thin inner layer 

 of the mantle. 



Itunning along the base of each arm 

 fera (after Francois), to show are two canals, a Small one at the base 



the definite arrangement of r. , , i • i 



the channels in the mantle : «, of the tentaclss, which we may term 

 position of mouth; b, posi- the tentacular canal, and a larger 



tiou of anus. ^ 



one, the canal of the lip. The 

 former sends a prolongation into each tentacle. The latter is, 

 according to Blochmann, a closed canal in Crania, Lincjula, Rliyn- 



Fiu. 315. — View of the iniier side 

 of a valve of Lingida anati 



