ARCHI-ANNELIDA. 615 



former drives the blood into the tentacles. The afferent tentacular vessel 

 is contractile, the efferent not so. The latter fuses with its fellow to form 

 the ventral vessel. Lacunae in the walls of the intestine put the dorsal 

 and ventral vessels in communication. The blood is feebly red when in 

 mass. There is a pair of nephridia in each fully developed somite, which 

 traverse the septa as in Oligochaeta and open laterally. The seven first 

 somites contain paired ovaries, the next succeeding testes. 



Two eye-specks and otocysts are stated to be present in P. ( = Poly- 

 gordius)flavocapitatus, and P. Schneideri. The former is also said to have 

 the coelome traversed by a network of connective tissue fibres, and 

 a special oviducal aperture in the last somite. 



The species of the genus Polygordius are larger than the species of 

 Protodrilus. P. lacteus is 40 mm. long, P. Villoti i dm. The cephalic tent- 

 acles are short, and at the apex of the prostomium. The posterior somites 

 are distinctly delimited. P. lacteus has the anus surrounded by eight 

 tooth-like processes, and a short distance in front of it the body is begirt 

 by a circle of twenty-four adhesive papillae. The cerebral ganglion in P. 

 neapolitanus is divided into three lobes, anterior, middle and posterior. The 

 oesophageal commissures originate from the middle lobe, and are united 

 on the ventral aspect by a transverse commissure. From this point onwards 

 there is a single median cord due to the fusion of the two larval cords. 

 Remnants of the ciliated longitudinal furrow which divides the two cords 

 of the larva are to be found within this cord as fine canals. The mouth is 

 ventral ; there is an oesophagus and ciliated intestine, the latter constricted 

 by the transverse septa. The blood-vascular system consists of a dorsal 

 vessel which gives origin in each somite to a pair of transverse vessels. 

 The latter end caecally with the exception of the first pair which are 

 united ventrally. The blood is red. There is a pair of nephridia in each 

 somite. The sexes are separate, and the genital products are developed 

 in the posterior somites. 



Perrier states that in P. Villoti the vicinity of the mouth, together 

 with a small part of the last somite are ciliated, that a ventral vessel is 

 probably present, and that the genital products escape by the nephridia. 



Protodrilus appears to develope direct (Repiachoff). Polygordius, on 

 the contrary, passes through a metamorphosis. The larva is a Trochosphere, 

 and the body grows as does that of an ordinary Chaetopod. There is 

 a pair of remarkable head-kidneys ; each consists (Fraipont) of a horizontal 

 ciliated intracellular tube terminating in a ciliated enlargement. A vertical 

 branch soon appears similarly terminated. The enlargements multiply 

 by division, and there are usually two to the vertical, three to the horizontal 

 branch. Each of them carries several radiating caecal tubules representing 

 aborted 'nephridial canals of the second order,' &c. (Fraipont). The 

 tubules in P. neapolitanus are supported by a funnel-shaped membrane 



