114 HESIONKLE 



Family VIII. — Hesionid2e (Sars). (Hesionea, Grube, 1851.) 



Head with two pairs of eyes, and two or three tentacles, and generally two 

 biarticnlate palpi. Nuchal organs primitive ; ciliated surfaces in direct contact with the 

 exterior (Racovitza). Body of moderate length. Pygidium with 2 anal cirri. Proboscis 

 protrusible, armed or unarmed. Anterior segments (1 — 4) distinct or more or less fused, 

 each carrying two pairs of tentacular cirri. The other segments uni- or bi-ramous ; 

 spines black ; superior division generally reduced, furnished with simple bristles ; inferior 

 division with compound bristles. Dorsal and ventral cirri filiform, faintly articulated. 



Segmental organ. — Hesione (Fallacia) has a very large genital funnel, not known to open 

 to the exterior, but connected at one point with the open segmental trumpet. Exit of 

 genital products has not been observed. In others, as in Ojohiodromus, at the moment of 

 reproduction the organ develops a large genital funnel for the transmission of the sexual 

 products (Goodrich). Fage, again, describes a cilio- phagocytic organ in connection with 



nc 

 Fig. 46.— Section showing muscles of Ophiodromus flexuosus, D. Ch. 



the segmental apparatus in Hesione pantheria, a form, however, in which it does not 

 transmit the sexual elements. 



It is interesting that Dr. Thomas Williams T long ago observed that the segmental 

 organs occurred in the hollow of the foot as a beautifully looped, extremely delicate, 

 slender, membranous ciliated tube. Further, that in the female the glandular yellowish 

 mass which spreads into the hollow base of the cirri and feet can be traced into organic 

 connection with the ciliated tube, and with that limb of the loop in which the vessels are 

 most developed. He considered that the ova passed into one of the limbs of the ciliated 

 tube. His description thus nearly approached the general structure as recently shown. 



In transverse section of the body-wall (Fig. 46) the dorsal longitudinal muscles are 

 thick externally and tapered to the dorsal median line. The ventral longitudinal muscles 

 are slightly curved and end abruptly internally against the somewhat large nerve-area 

 which has the oblique muscles inserted dorsally, whilst externally are the hypoderm and 

 cuticle. This family, therefore, agrees with Nephthys in the relations of the nerve-area. 



1 ' Philos. Trans./ 1858, p. 127, pi. viii, fig. 21. 





