On the Structure and Development of Argiope. 519 



of theliver and the ovaries can be seenthrough the semi-transparentdisk 

 of the lophophore. 



Diagiainatic view of the muscles of Argiope. 



Section of a single tentacleshowing the ciliated epithelium onthreesides, 

 and the central canal containing musele fibres. Zeiss F. 



View of the rounded inner ends of the calcareous spicules of the shell, 

 with some mantle papillae. Zeiss A. 



A section through the point of attachment of the lophophore to the mantle 

 lining the dorsal shell. The mantle papillae are seen piercing the shell 

 and are connected with cuticle upon the outer side. The ciliated groove 

 formed by the lip and the tentacles is shown and the cushion of high epi- 

 thelium cells. In this section the communication between the canal run- 

 ning round the edge of the lophophore and the canal in the tentacle is 

 not shown. 

 Fig. 16. View of the interiorof the dorsal'shell of an Argiope neapolitana, to show 

 the arrangement of the internal skeleton supporting the lophophore. 



Fig. 17. View of interior of ventral shell of the same, showing the median ridge, 

 and the triangulär areas whose apices fit into notches in the dorsal shell 

 and so form the hinge. 



Fig. 18. Lateral view of dorsal Shell. 



Fig. 19. View of the organic fibres, in whose meshes the calcareous spicules of the 



Shell lie. 

 Fig. 20. Ovum. 



Fig. 21. Ovum of two Segments. 

 Fig. 22. Ovum of three Segments. 



Fig. 23. Blastosphere ; by the side are some cells oftbe blastosphere more highly 



magnified. 

 Fig. 24. Gastrula. 

 P'ig. 2b. Larva of two segments showing the stalk attaching it to the walls of the 



brood pouch. 

 Fig. 26. Larva showing traces of three segments with eyespot and commencing 



bristles. The outline of the alimentary canal is seenfaintly. 



Slightly older larva. 



Larva with the two kinds of cilia on the first segment. The second Seg- 

 ment has already begun to grow down over the third which has con- 

 stricted slightly into two parts. 



Free swimming larva seen from the ventral side. 



Free swimming larva seen laterally. 



Young Argiope, the lophophore stili circular, with twelve tentacles. The 

 liver is growing out as two lateral diverticula of the stomach. 



View of the ventral shell of the same. 



Longitudinal section through a larva of about the same stage as fig. 27. 

 This shows the alimentary canal extending through ali the segments. 



34* 



