4 OPHELIICLE. 



Sections of the segmental organ occur in that portion of the coelom between the lower 

 border of the oblique muscle and the ventral longitudinal, and to the exterior are 

 attached groups of early ova. The duct from the organ opens to the exterior on the 

 outer and upper border of each ventral pedicle, and, so far as appearances go, near the 

 bristle-tuft, and in certain forms near the cirrus (branchia). 1 At least stained granules 

 had exuded at this point, and though the hypoderm is thickened over an area below the 

 bristles, no aperture could be demonstrated. From the size of the canal it would seem 

 to be capable of transmitting the ova. In the specially thickened cuticle of the arch and 

 inner sides of the ventral pedicles, fan-like processes passed from the hypoderm to the 

 surface in groups of five or six or more, as if pores existed at these points. Occasionally 

 they occurred in the thick cuticle on the outer surface of the pedicle. These may, 

 however, have been due to the effects of preparation, but their regularity is interesting. 



Fig. 98.— Transverse section of the body- wall of Ophelia limacina, H. Kathke. 



A still further modification occurs in Ammotrypane 2 (Fig. 99) in which the oblique 

 muscles seem to have split into two divisions, the upper (o.ra.), much modified, passes 

 straight across the narrowed body-wall from side to side and separates the ventral lobes 

 containing the ventral longitudinal muscles and other parts, whilst a short but powerful 

 slip {p.m.') extends from the lateral margin on each side of the nerve-area to the opposite 

 edge of the raphe of the ventral longitudinal muscle and to the firm wall at its inner 

 border. Such, perhaps, may represent only a continuation of the metamorphosed 

 oblique muscle which is prevented from joining the other fibres by the nerve-area in the 

 centre that abuts closely on the lower fibres of the muscle of the pedicle, and, besides, 

 a thin hypodermic area has an incurvation, with the cuticle ventrally, at each side. A 

 distinct neural canal occurs at the upper end of the nerve-area. The lateral region is 



1 Ophelia A, c Valorous ' Exped. 



2 f Proc. Roy. Soc. Edinb./ vol. ix, 1876-7, p. 377, 



