380 Mr. H. N. Moseley on a Young 



nerve-ganglia the vascular trunks are enlarged into wide reser- 

 voirs. No branches of these vessels were seen ; and though 

 the animal was living when examined, no pulsation in them 

 was observed. The vessels had a pellucid wall, in which were 

 imbedded elongate oval nuclei (fig. 4, b), but which otherwise 

 appeared structureless. No motion of any fluid within the 

 vessels was seen. 



Although the specimen under description was evidently so 

 immature, well developed ovaries were present, the specimen 

 being a female, as was the adult one before obtained. The 

 ovaries follow in their disposition the vascular trunks so closely 

 as to appear as if connected with them. The ovaries are 

 simple ovoid sacs with a distinct wall (fig. 2), filled with ova 

 (in various stages of development) and granular matter. A 

 dark irregular fissure appeared on the centre of each ovary as 

 viewed from the dorsal surface, which I believe to be an open- 

 ing by Avhich the cavity of the organ communicates with the 

 exterior, thus dorsally. The ovaries were not quite regular in 

 disposition, an extra anterior one being developed on the right 

 side of the body. In the interspace between the most anterior 

 and larger pair of intestinal diverticula and the next posterior 

 pair were four pairs of ovaries, whereas in the succeeding cor- 

 responding interspaces were only single pairs of these organs. 

 In the adult specimen described in the 'Annals ' (March 1875), 

 a single ovarian sac only was present in each interspace be- 

 tween the diverticula of the digestive tract. It would there- 

 fore seem probable that on further development three pairs of 

 diverticula would have budded out between the first and second 

 pairs in the present specimen. 



The muscular system consists of a series of excessively fine 

 transversely or circularly disposed fibres, which are external 

 in position to a series of broad band-like longitudinal muscles. 

 The longitudinal muscular bands are in close relation with the 

 proboscis-sac. Their exact disposition was not made out, and 

 their arrangement as shown in the figure will possibly need 

 correction. 



On the whole, Pelagonemertes is a form of considerable 

 zoological importance. 



In the flattened form of its body and in its dendroccelous 

 digestive tract the animal resembles Planarians. Amongst 

 the Rhabdocceles the Prostomeae possess an exsertile proboscis 

 like that of Nemertines ; but such an organ is present in no 

 Dendroccele. In all particulars — in being unisexual, in the 

 simplicity of the generative organs, in the form of the nervous 

 and vascular systems and of the proboscis, in the position of 



