506 Arthur E. Shipley 



Hancock in bis great work oii the Brachiopoda states that ali the 

 niiiscles are unstriated with the exceptiou of the posterior Occlusor, 

 which is striated. This is eonfirmed by Van Bemmelen who siiggests 

 that in this arrangement of a muscle with a double orìgin (the fibres of 

 one part being striated, and of the other unstriated'i and a single Inser- 

 tion, we find a provision for the voluntary and involuntary closure of 

 the shell. In Argiope I can see no trace of striation in the posterior half 

 of the Occlusor muscle which exactly resembles the remaining muscles. 



The peduncle of Argiope appears to be an uuusually large devel- 

 opment of the homogeneous supporting substauce which occurs so fre- 

 quently in the body of Brachiopoda. It is in dose organic connection 

 with both Shells (fig. 1 P) and its free end is very irregulär, being pro- 

 duced into papillae, which enter any depressions occurring on the rock 

 upon which the animai lives. Externally it is coated by a layer of cu- 

 ticle, within this is a layer of cells, the epidermis. The remainder of 

 the peduncle consists of the homogeneous basement which stains well, 

 and which contains three different elements. The first of these are a 

 number of branched, granular, nucleated cells whose branches form a 

 network in which the supporting substance lies. The second consists of 

 numerous fibres which take a longitudinal course in the centre of the 

 stalk ; their lower end is very fine, and is often crumpled as if the stalk 

 had shortened. The remaining structures met with in the stalk consist 

 of some very peculiar ovai bodies, these seem tobe crammed with round 

 cells somewhat resembling the blood corpuscles. These bodies are often 

 connected with the lower end of a fibre. They are irregularly distri- 

 buted but occur chiefly near the circumference. It is possible that they 

 are connected with the secretion of the cement which glues the Argiope 

 to its support. 



Owing to the small size of Argiope , it is impossible to dissect out 

 the nervous system, so I bave been obliged to study it solely by meaus 

 of sections. The centrai nervous ganglion is sub-oesophageal and lies 

 in the epidermis. It is situated in that part of the body wall which lies 

 immediately posterior to the base of the tentacles which overhang the 

 mouth fig. 1 sg) just where the body wall turns forward to form the 

 mantle lining the ventral shell. The ganglion consists of two parts. The 

 anterior is a well marked elevatiou, formed by a ridge of the homo- 

 geneous supporting substance, so often mentioned, which is covered by a 

 layer of nervous cells and fibres. The posterior is simply a narrow band 

 of nervous tissue. not very conspicuous. The ganglion extends the whole 

 breadth of the body wall, which in this Situation is not very great, having 



