8o 



A n a t o m i c a 1 R e m ar k s. 



The anatomy of this genus has been studied by Cuvier '), Eschricht "), Souleyet ^), 

 Wagner ■'), Pelseneer °) and Schalfejeff ^). I have thought it better to give a few notes with 

 respect to the central nervous system about which Pelseneer gave a most detailed description. 

 As I differ froni hini in a few points, I cannot let them pass in silence. I have examined some 

 specimens of Clionc /iiimcina (Leyden Museum). 



The central nervous system of Clionc is constituted like that of the Pneumonodermatidae, 

 viz. the form and disposition of the ganglia is nearly quite the same. In Clionc, the pleuro- 

 visceral connective is a little shorter, and the pedal ganglia present a long commissure (which, 

 however, does not alwaj-s occur). 



I. The cerebral ganglia (PI. V, fig. 144) are situated above the oesophagus, and exhibit a 

 distinct commissure. Three pair of connectives issue from them. 



A. From the oesophageal surface of each ganglion a thin connective [bc^ passes to the 

 buccal orangrlia. 



B. From the lateral .side a .strong connective (/^) goes to the pedal ganglion. 



C. A little more distally, nearly parallel to the foregoing one a cerebro-pleural connective 

 [plc] is discernible. 



The last two connectives are longer than in the Pneumonodermatidae. 



From each cerebral gfanelion several nerves arise. 



From the dor.sal part two nerves (i, 2) proceed to the nuchal tentacle. They 

 are the olfactory and the optie nerve, both ending in a swelling. The optie nerve (2) 

 exhibits at its base a ganglionic enlargement, readily visible. An attentive exaniination 

 shows, that it consists of two elongated swellings (fig. 145), each with a large nucleus. 

 This fact seems not to have been observed before. I could not discover an anastomosis 

 between the two nerves, but such a connection has been mentioned by Boas ^), who studied 

 it in Clione. 



P'rom the lateral side of the cerebral ganglion, a little ventrally, a nerve (fig. 144, 3) 

 passes to the otocyst. 



I have seen two large trunks arising from the front part of the cerebral ganglion. 

 The lateral one soon divides into two branches, each of which sends off a slender nerve 

 to the skin (4, 5). The lateral branch (4) innervates the ventral buccal cone; the median 

 (5) goes to the labial tentacle. The median trunk equally divides into two nerves (6, 7), 



i) Mémoiie sur Ie Clio borcalis. Ann. Mus. crHi.-^t. Natur. vol. II (1802), p. 242 — 249. 



2) Anatomische Unteisuchungen iiber die Clionc borcalis (1838). 



3) Voyage de la Bonite, vol. Il, p. 275 — 288, pi. XV, figs. i — 17. 



4) Die Wirbellosen des Weissen Meeres. Bd. I (1885), p. 89 — 120. 



5) The cephalic appendages of Ihe Gymnosomatous Pteropoda, and especially of Clionc, Qiiarterly Jouin. Mier. Sci. (18S5), 

 vol. XXV, p. 491 — 507, pi. XXXV, and Recherches sur Ie système uerveux des Ptéropodes, .\rch. de Biol., vol. VII, p. 96 — loi, 

 pi. IV, figs. 1—4. 



6) Zur Anatomie der Clionc liniacina. Zool. Anz., Jahrg. XII, p. iSS — igo. y 



7) Spolia atlantica, p. 143. 



