328 EDWARD S. MORSE ON 



sheath. A transverse section of the peduncle in alcohol shows the outer tube naade up or 

 a series of concentric layers, next a thickened cellular lining, and then a thin membrane 

 from which spring fine fibres of connective tissue (43: ll). Another transverse section 

 (43 : 12) 'from a preserved specimen shows a series of folds of the inner cavity. In 43: 5, 

 is presented the appearance of the peduncle of Glottidia in life, and a somewhat complex 

 structure of the parts is indicated. Thus the outer sheath, which seems almost structure- 

 less, is, at times, thrown into distinct and regular annulations ; the annulations of the 

 inner tube alternate with those of the outer tube, and the crests of these inner 

 annulations seem to send minute processes into the outer tube. This appearance is prob- 

 ably due to a wrinkhng of the substance. In 43 : 10 is shown a columnar epithelium on 

 the outer surface of the middle tube; 43: 4 shows very clearly the retraction of the inner 

 tube, leaving a distinct space between its end and the end of the peduncle, which is 

 enlarged and irregularly folded. The mobihty of the peduncle even at its thickest por- 

 tion and the manner in which the beaks of the shells impinge on its substance are illus- 

 trated by 43: 13. The peduncle of L. anatina is quite opaque and but little could be 

 seen through its walls. In Glottidia and L. lepidula the peduncle is somewhat translu- 

 cent and the circulation of the blood within gives it a rosy hue. 



A figure of the peduncle of D. lamellosa is given in 43 : 14. The various muscles 

 here shown certainly indicate great mobility of the body upon its stalk. 



The peduncle of Terebratulina has been most exhaustively treated by Ekman ('96) , 

 and so, for comparison only, I have ventured to give one figure illustrating the peduncle 

 from a small specimen of T. septentrionalis (43 : 15) . I have shown elsewhere that in 

 the extreme young of Terebratulina, the peduncle is elongated, exceeding the length of 

 the shell, and with the elongated shell gives it a very linguloid appearance. In later 

 stages it becomes shorter and sends out a number of processes which have been fully 

 figured and described by Ekman in the memoir above referred to. 



Setae. 



A very characteristic feature of the Brachiopoda is the setae which fringe the 

 borders of the pallium. These vermian hairs arise from true setigerous follicles which are 

 immersed at various depths in the thickened liorders of the pallium. In the errantian 

 forms they are highly mobile and act, as in the annelids, as locomotive organs ; in Disci- 

 nisca, they are variously barbed and in the extreme young of all forms thus far examined, 

 the setae are not only barbed but deciduous. The setae of brachiopods differ from 

 those of most chaetopods in not being jointed. Among the chaetopod annelids, however, 



