498 Arthur E. Shipley 



canal but, imlike that, is closed at its outer end. The walls of the tube 

 consist of a striietureless membrane which stains well and appears to 

 consist of the same tissue as the org'anic network of the shell. The fìbres 

 of the latter in the neighbourhood of the tube fuse with it. The outer 

 end of the tube is slightly enlarged and the outer wall which closes it 

 is much thicker than the lateral walls. There appears to be a dose con- 

 nection between the top of these papillae and the periostracum. for in 

 many cases when the latter was torn away elsewhere it remained atta- 

 ched to the summit of the papillae. The periostracum passes unchanged 

 over the summit of the papillae but a'|number of fine lines appear to 

 pass from the underside of the periostracum to the top of the papillae 

 (fig. 15). 



Within these papillae lie freely a number of round bodies , w^hich 

 stain deeply especially at their circumference. These bodies are gene- 

 rally aggregated in small Clusters, two or three such aggregations often 

 being found in one papilla. These bodies agree very exactly with the 

 blood corpuscles which are seen in sections of the blood vessels running 

 in the mantle. In many cases I bave been able to see that the cavity of the 

 papillae is in communication with that of the blood vessels and in some 

 sections I bave seen a bündle of corpuscles lying half in the blood vessel 

 and half in the lumen of the papilla, therefore I believe the bodies in the 

 papillae to be simply blood corpuscles and that the lumen of the papillae 

 are in direct communication with the blood system. 



There has always existed a great deal of doubt as to the nature and 

 function of the mantle papillae. Van Bemmelen has seen the bodies de- 

 scribed lying in the papillae, and has come tothe conclusion that they are 

 the deeply stained nuclei of fiat epithelial cells lining the cavities. It not 

 difficult as far as Argiope is concerned, to demonstrate that this is not 

 so. In this Brachiopod the papillae are unusually large; in longitudinal 

 sections it is seen that the bodies are very irregularly scattered , some- 

 tìmes the canal is choked with them, sometimes there is only one hundle 

 which may lie at eather end or in the middle, in other cases there are 

 none ; in transverse section it is seen that the corpuscles lie in the centre 

 and do not line the walls. Furthermore no trace of cells can be seen 

 lining the canals (fig. 15 mp). 



Hancock ^ has noticed the resemblance existing between these 

 bodies and the blood corpuscles , but as he did not believe that the pa- 

 pillae possessed any respiratory functions, he concluded that the bodies 



1 Oa the orgaüisation of theBrachiopoda. Phil. Trans. Voi. CXLVIII. Partii. 



1858. 



