ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 225 



union of the nephridial tubes of one pair on the back, and the presence 

 of a common unpaired efferent duct are, so far as the author knows, pecu- 

 liarities which are confined to these two families. For the complete 

 understanding of the significance of these- points, a number of other 

 organs will have to be taken into consideration ; this the author promises 

 to do. 



Nervous System of Chaetopterus Valencinii.* — M. J. Joyeux- 

 Laffuie finds that it is not, as many writers have stated, difficult to 

 dissect out the nervous system of Chsetopterus ; it is only necessary to 

 keep specimens for some time in preserving fluids. In the median and 

 lower regions the nervous centres are represented by a double ganglionic 

 chain placed in the integument at the bottom of a groove formed by the two 

 large ventral muscles. In each segment there are two symmetrical and 

 fusiform ganglia, separated from one another in space, and connected 

 by several very short commissures, the number of which is ordinarily 

 seven or eight, but varies in different segments. Each ganglion gives 

 off several nerves, three generally going to the neuropodium, and three, 

 larger, to the notopodium. 



In the superior region of the body the arrangements are very different. 

 The connectives from the first pair of ganglia of the median region 

 separate to form the two large nerve-cords ; these cords are formed of 

 two apposed bands, of which that which is ventrally placed is solely 

 formed of nerve-cells, and the other of fibres with a few nerve-cells ; the 

 former represents the ganglia which appear to be wanting, and the 

 latter the connectives ; there are no isolated ganglia. 



Contrary to what is usually stated, the author asserts that these cords 

 give off on each side a number of nerves, and indeed, the superior region 

 of the body of Chsetopterus is that which is best supplied with nerves. 

 The two cords are connected together by commissures. In addition 

 to the optic and tentacular nerves already described as being given off 

 from the dorsal part of the nerve-cords there are several others ; of these 

 the most important are the three pairs of buccal nerves which give the 

 buccal infundibulum its great sensibility, and a j)air of nerves distributed 

 on the dorsal surface of either sido of the vibratile groove. 



The constitution of the apparently anomalous nervous system of the 

 upper part of Clisetopterus may be thus summed up ; a dorsal and cerebroid 

 part with nerves for the organs of sense, a ventral part formed of nerve- 

 cells representing the ganglia, nerve-fibres which form connectives, and 

 numerous commissures connecting the ganglionic parts. 



Polygordius.f — Prof. J. Fraipont deals with the genus Polygordius 

 in the 14th monograph of the Naples Station. 



I. Structure. — After describing observations on the living worm, and 

 the general external characters, he gives a detailed account of the 

 anatomical and histological structure. The thick elastic cuticle, delicate 

 near mouth, anus, tentacles, &c. ; the subjacent hypodermis, thick and 

 glandular in the cephalic lobe of the first segment and in the last, and 

 with brick-red pigment in P. neapclitanus ; the yellowish clear layer of 

 longitudinal muscles ; the subjacent irregularly thickened granular layer 



* Comptes Rendus, cvi. (1888) pp. 148-516. 



t Fauna unci Flora des Golfes vou Neapel, xiv. Monogr., 1887, pp. 1-127 

 (16 pls.> 



