STRUCTURE OF BRACHIOPOBS. 



191 



Fig. 130.— Ampullaj of blood 

 fimu>e8, phowina; course taken 

 by the blood. — After Morse. 



blood courses in 

 and down these 



but with no ganglionic enlargements, except in Discina, 

 where they terminate each by a ganglion in the last two 

 posterior muscles. Morse has discovered the presence of 

 auditory capsules in Lingula. 



Respiration is mainly carried on in the mantle (pdlial 

 membrane). In Lingula the pallial membrane is divided 

 into oblique transverse sinuses, which 

 run parallel to each other. From 

 these arise, says Morse, numerous 

 flattened ampullae, which are highly 

 contractile. The 

 regular order up 



sinuses, entering each of the ampullae 

 in turn. Fig. 130 represents a row of five ampullae with in- 

 dications of the course taken by the blood-disks. These 

 ampullae have not been found in Discina, though the pallial 

 sinuses are very prominent. The breathing process is also 

 carried on in the tentacles or cirri. 



Intimately connected with the vascular system is a gland- 

 ular portion of the tubular part of the segmental organs of 

 the BracMopoda, which is 

 supposed to represent simi- 

 lar parts in worms as well 

 as the glandular, excretory 

 portion of the organ of 

 Bojanus in mollusks, and is 

 supposed to be depuratory 

 or renal in function. 



The reproductive system 

 of BracMopoda consists of 

 ovaries, oviducts or seg- 

 mental organs, Fig. 131, 

 and spermaries. The sexes 

 are probably separate in all BracMopoda (Morse). 



The ovaries are attached in Discina and Lingula to the 

 delicate vascular membranes of the large sinuses in the pal- 

 lial membranes, the vascular membranes being thrown into 

 conspicuous ruffs when the eggs are ripe. In Terebratulina 

 and Rhynchonella they are not only similarly situated, but 



Fig. 131.— Segmental organs of Brachio- 

 ods. a, Discina ; 6, Terebratulina.- After 

 lorse. 



