On the Structure and Development of Argiope. 507 



beeu reduced by the lateral invaginations wbich form the brood pouches. 

 The posterior band of nervous cells gives off a brancb on each side which 

 passes to supply the occlusor muscles, entering them where their tendon 

 has fiised with the supporting siibstance beneath the ganglion ; it also 

 gives off laterally two braiiches which pass to the mantle of the ven- 

 tral shell. The niain ganglion gives off two branches which enter the 

 lophophore, one on each side, and which, I believe, run entirely round 

 the edge of the lophophore beneath the cìliated epithelium cushion at 

 the base of the tentacles , thus forming a circum-oesophageal ring. At 

 each end the principal ganglion divides into two branches ; one of these 

 passes backward in the body wall in the line of attachment of the gastro- 

 parietal band into which some small branches pass. The other branch 

 circumscribes the Oesophagus, the nerves being imbedded in the support- 

 ing substance of the lophophore , above the Oesophagus they come to 

 the surface again and enter an elongated ganglion which lies in the ecto- 

 derm just anterior to the base of the lip which overshadows the mouth. 

 This ganglion is very small in comparison with the sub-oesophageal. 



The ganglion consists chiefly of unipolar ganglion cells whose pro- 

 cesses pass into the long fine fibres which compose the nerves. 



The nerve cells He upon a thick cushion of supporting substance 

 and the nerves are very usually imbedded in the same tissue. 



Van Bemmelen also describes a nerve which coming from the 

 supra-oesophageal ganglion, also supplies the lophophore. I bave not 

 been able to find this branch in Argiope. 



Although I bave not been so fortunate as to find a male Argiope, 

 yet I bave no doubt that this genus like the other members of its class 

 which bave been described, is dioecious. In those Argiopes which I 

 bave examined, I find no trace of a testis, and in the allied genera Theci- 

 dium, Lacaze-Duthiers ^ describes the male genital gland in a position 

 similar to that occupied by the ovary in Argiope , and I bave myself 

 seen the testes of Megerlea in the same position. 



The ovaries of Argiope are of a bright brick red color resembling 

 the red rays on the shell of Argiope cuneata. There are found two lying 

 in the body cavity of the dorsal shell and two in that part of the body 

 cavity which is produced into the mantle lining the ventral shell. The 

 latter pair are not always developed in Argiope neapolitana. The ova- 

 ries of the dorsal shell are at their anterior end enclosed on one side by 

 the body wall lining the shell and on the other by a mesentery which is 



' Histoire de^la Thécidie. Auuales des Sciences Naturelles. 4meSér. T. XV. 

 1861. 



