Minot.] 20 [November 15, 



of the ventral nervous cord of Annelids, out of the union of two 

 lateral nerves, is rendered very doubtful; for the theory started from 

 the supposed existence of such nerves in Turbellarians, the so-called 

 lowest worms. The reproductive system reveals equally noteworthy 

 differences. The Nemertines are dioecious, the sexual glands are 

 small, and arranged in equidistant pairs; there is no special efferent 

 duct with several specialized parts, as in the Plathelminths, but the 

 sexual products are discharged by the bursting of the walls of the 

 gland sacks in which they are developed. The yolk glands, for 

 which I propose the more appropriate name of egg-foodstocks, or 

 more simply foodstocks (Einahrungsstocke), are very characteristic 

 of the whole class, except the Neinertines, where they are utterly 

 unknown. The Nemertines have a circulatory system, with three 

 principal longitudinal vessels having special muscular walls — while 

 they have no water vascular system; while just the reverse is true 

 of the genuine Plathelminths, which have no blood vessels. The 

 digestive canal of Nemertines is formed by a strongly differen- 

 tiated oesophagus and a straight tube having an anus posteriorly. In 

 the Plathelminths there is no distinct oesophagus, though there is 

 often a muscular pharynx, which the Nemertines never possess. 

 Their supposed nearest relatives, the Dendrocoela and Ehabdocoela 

 (in part), have a prehensile proboscis connected with the mouth, but 

 are without any anus. Finally, the proboscis of the Nemert'nes is 

 still a morphological mystery; it is contained in a sheath that lies 

 over the digestive canal, and passes through the nervous ring. There 

 is no similar structure known among Plathelminths, unless it be the 

 proboscis of Prostomum. I have endeavored elsewhere 1 to show 

 that there is no correspondence yet proved. 



These differences seem to me sufficient to render the removal of 

 the Nemertines from the class of the Plathelminths unavoidable. 

 Where they belong is another question which I cannot answer; there 

 are indications of a relationship with the Annelids. It is to be hoped 

 that Prof. Semper will discuss this question in his forthcoming 

 memoir. 



The remaining forms are so closely related that their more import- 

 ant characteristics may be easily summed up in general terms. The 

 epidermis is formed of epithelial and glandular cells, resembling those 

 of leeches; there is a thin cuticula, and a thick fibrous basement 

 membrane, which is very characteristic, and separates the muscular 



1 Semper's Arbeiten. Bd. in, Hft. 4. 



