LIVING BRACHIOPODA. 363 



or in L. lepidula but is more flaring and the rim is slightly undulating. The body of the 

 nephridium is held to the perivisceral wall by a narrow band immediately behind the 

 obliquus internus, and this may be a continuation of the ilio-parietal band. A greatly 

 enlarged view of the nephrostome and a portion of the nephridium is given in 55 ,■ 2. It is 

 seen to be highly vascular ; large branching lacunae run from the base of the nephrostome 

 to the periphery ; these divide, and just before reaching the rim they appear, in the drawing, 

 to be recurved. This appearance is due to the incurving edge of the flaring rim which is 

 very thin and transparent. The lacunae have a delicate light brown tint. The ciliated 

 ridge is seen running in the centre of each lacune and the blood follows up and down the 

 branches, the current being divided by this ridge. In the undetermined species of 

 Lingula, the nephrostomes were turned toward the perivisceral cavity (40 : 18) . Whether 

 during genital activity the nephrostome has the power of turning in this way, is not 

 known. In D. lamellosa (55 : 3) the nephridium, while occupying a position similar to that 

 in the lAngulidae, is quite different in its attitude. The nephrostome is turned towards 

 the coelomic cavity and obliquely toward the dorsal shell. It is wide and flaring with 

 regular radiating folds running from the inside nearly to the periphery. It is held to the 

 lateral body wall by a band which seems continuous with the membrane composing the 

 nephrostome. This flaring mouth connects at once with the tubular portion of the 

 nephridium without the usual constriction seen in the nephridia of other forms and there 

 is no glandular enlargement or thickening. The tube tapers gradually to its termination 

 in the anterior wall of the coelomic cavity. These openings are seen externally just 

 below the mouth on each side and about midway between the dorsal and ventral parietes. 

 The external openings stand oblique and incline to each other (55 : 4) . A view from 

 within this wall shows that the tubes follow along the ventral floor of the coelomic 

 cavity and then turn upward along the body wall, piercing the wall obliquely (55:5). 

 Externally the openings are as simple as in L. lepidula. In the early stages of D. 

 lamellosa, the nephridium has a long, narrow nephrostome suggesting somewhat the 

 appearance of the same part in Crania as figured by Joubin, though his figure represents 

 the nephrostome as bifurcated. The edge appears to be minutely fringed and the tube 

 shows a slight enlargement in its course (55 : 6) . The small circle associated with the 

 figure indicates the size of the specimen from which the nephridium was drawn. 



We have seen in the Lingulidae a constancy in form and position of the nephridia 

 quite in accordance with those resemblances in structure seen in all the parts. In 

 Discinisca, the nephridia are quite unUke those of the Lingulidae, as is the animal itself. 

 Crania stands quite apart from all in the form of this organ. In the Testicardine 

 Brachiopoda, the nephridia vary from one another quite as much as does the internal 

 structure of the different forms, or the external appearance of their shells. 



