700 



THE ANIMAL KINGDOM. 



lateral gastro-parietal bands, and their external apertures are above, i. e. 

 dorsal or anterior to the bases of the two arms. 



The sexes are certainly separate in Crania among Ecardines, and in 

 many Testicar dines. Beyer, the most recent investigator of Lingula 

 (L.pyramidata\\\-a.s come,, like his predecessors, to the conclusion that it is 

 hermaphrodite ; Schulgin and Shipley, who have investigated Argiope, 

 have seen none but females. As to Ecardines the genital organs of 

 Discina are attached in groups, some to the lower edge of the lateral 

 gastro-parietal bands, others to the ileo-parietal bands at their origin 

 from the stomach. In Lingula anatina and L. affinis there is a set of 

 dorsal and of ventral glands suspended to the ileo-parietal bands. 

 L. ' pyramidata however agrees with Crania and other Brachiopoda in 

 which the glands, two dorsal and two ventral, are contained in the 

 trunks and main branches of the pallial sinuses, but extend sometimes 

 to a greater, sometimes to a less degree into the central portion of the 

 coelome. They are usually attached to the outer aspect of the sinuses, 

 more rarely to the inner, i.e. the side towards the shell as in L. pyramidata 

 and Argiope. They consist essentially of a process of supporting substance 

 which grows out into lamellae, very numerous in the case of the testis, 

 excavated by cavities, and covered superficially by an epithelium. The 

 supporting substance is continuous with that of the wall of the sinus, the 

 epithelium with the coelomic epithelium lining it. From the epithelium 

 are derived both sperm-cells and ova. The striated corpuscles found in 

 the blood of Lingula are said to be spermatophores. Impregnation probably 

 takes place after the escape of the ova. The latter during their growth 

 (? in L. pyramidata) are surrounded by a layer of small cells, probably 

 abortive ova. 



The Brachiopoda are found in all seas. The greatest number live 

 at moderate depths down to 100 fathoms ; few range to 500 fathoms ; 

 but Discina atlantica occurs between 690-2400, and Terebratula Wyvillii 

 between 1035 and 2900. Some species exist at very varying depths, e.g. 

 Terebratula vitrea from 5 to 1456 fathoms. Lingula and Glottidia live at 

 about half-tide marks, and extend down to seventy fathoms. They bury 

 themselves in mud, and their peduncle agglutinates a sand tube. When 

 the shell of the living Lingula is open, the mantle-folds are disposed so as 

 to form an aperture on either side through which water enters, and a 

 single central opening by which it escapes. These openings are converted 

 into funnels by the prominent setae fringing the mantle edges. The 

 majority of Brachiopoda attach themselves to rocky bottoms. The 

 animals occur in great numbers wherever they are found. 



Of living genera Lingula and Discina range from Cambrian strata to 

 the present time, Discinisca, Crania (?) and Rhynchonella from the middle 

 Silurian, Crania and Terebratula from Devonian, Thecidium and Wald- 



