504 Arthur E. Shipley 



the dorsal shell. The blood eorpiiscles are large in comparisou with the 

 other cells of Argiope , which like ali Brachiopod cells are extremely 

 small. They stain deeply at their eirciimference aud appear to possess no 

 nuclei, and usiially He together in small Clusters. Although owing to 

 the presence of the shell it is impossible to observe the blood circulating, 

 we must conclude that it does so by the contractility of the vessels, 

 since there is no^entral propelling organ. 



I bave mentioned above the arguments which exìst against the 

 view that the function of respiration is carried on either by the tentacles 

 of the lophophore, or by the papillae of the shell. I believe that respi- 

 ration takes place in the mantle lining the shell, especially the perforate 

 shell where a large area is coustantly exposed to the currents of water 

 which are set up by the action of the ciliated tentacles. The mantle is 

 penetrated by a network of vessels, in which the blood is separated only 

 by a very delicate sheet of tissue from the water , and I believe there 

 cannot be much doubt that the amount of oxygen required by such a very 

 inactive animai as Argiope can thus be easily obtained. This view is also 

 supported by the fact that in Lingula respiration is carried on by the inner 

 lining of the mantle which bears the well known respiratory ampullae. 



The muscles of Argiope consist of four pairs ; of these two pairs 

 are connected with the movement of the shell upon the stalk , the other 

 two with closing and opening the shell. Each of these last is composed 

 of two parts and is usually considered to represent two distinct muscles, 

 thus making the number six, which number was described by Hancock 

 as typical of the Testicardinate Brachiopods. In describing the muscles 

 I bave adopted the nomenclature proposed by Hancock. Of the two 

 pairs of adjustors which are both inserted into the peduncle , one pairs 

 arises from each shell (fig. 12 d.ad. and v.acL). The pair arislng 

 from the dorsal shell has its origin opposite the commencement of the 

 intestine , and the muscles of this pair are dose to each other , one 

 on each side of the median line ; they pass down and are inserted by 

 a tendinous cord which passes directly into the substance of the stalk. 

 The adjustors of the other shell bave their point of origin a little nearer 

 the posterior border of the shell and arca rather larger , they also are 

 inserted into the stalk in a similar manner. The i)rincipal function of 

 these muscles is without doubt to raise and lower the animai upon its 

 stalk. Hancock suggests that they also serve to rotate the animai by 

 the muscles of each side alternately contracting, but as the origius 

 of the muscles are so dose to one another and also their insertions, and 

 as the muscles are parallel , I do not tliink this Suggestion very pro- 



