1880.] NATURAL SCIENCES OF PHILADELPHIA. 93 



three distinct commissures, which are nearly as long as the diameter 

 of the ganglia. From the outer part of the right visceral ganglion 

 issues a nerve nearly as long as the transverse diameter of the whole 

 central nervous system and swelling to a rather large ganglion (gangl. 

 penis) at the root of the penis ; this ganglion contains only rather 

 small cells and gives off three or four strong and several thinner nerves 

 (Plate X, fig. 15). The part of the brain which gives off the nervus 

 opticus, simulates a ganglion. The proximal ganglia olfactcia bulbi- 

 form, somewhat smaller than the buccal ganglia, but much larger than 

 the distal ganglia olfactoria ; the buccal ganglia flattened, rounded, con- 

 nected by a rather short commissure ; the ganglia gastro-oesophagalia 

 rounded, having about one-fifth of the size of the last, containing one 

 very large cell and a few smaller. 



The eyes with black pigment and yellowish lens. The otocysts 

 lying at the hinder part of the cerebral ganolia, as large as the eyes ; 

 with numerous small otokonia, which in the specimens from Kiel, 

 were not much calcified. No trace of spicula in the leaves or other 

 parts of the riiinophoria. The spicula of the skin were, so to speak, 

 limited to the margins of the mantle and of the foot ; in the last they 

 were chiefly arranged perpendicularly or obliquely against the margin, 

 except that in the foremost and hinder part of the sole some few spic- 

 ula were seen scattered. 



The amount of spicula in the skin seems to vary notably in the 

 Acanthodoris piJosa, as seems to be the case in general in different 

 forms of Dorididce, especially, as far as hitherto known, in the Poly- 

 ceratidce {Polycera, Ancula). (Cf. Meyer and Moebius, Fauna der 

 Kieler Bucht, I, 1865, pp. 52, 60.) Frey and Leuckart (Beitr. zur 

 Kenntn. wirbellose Thiere, 1847, p. 145 ; described a very regular 

 position of the spicula, but not, as it seems, in accordance with nature. 



In the margin of the mantle the spicula were arranged as figured by 

 Alder and Hanc., 1. c. Part VII, PI. 48, supplem. fig. 1, only more con- 

 centrically at the transition from the margin to the side of the body; a 

 narrow belt of spicula crossed the back before the region of the gill. 

 Some spicula were also seen in the tentacles. The spicula reached a 

 notable length (at least 0.6 mm.^, in old individuals they were more 

 calcified than in younger ones. The skin was filled with unicellular 

 glands, especially in the dorsal papilla?.' 



The mouth-tube was wide and strong, about 1.5 mm. long; the 

 bulbus pharyngeus in the largest individuals about 2.75 mm. long, by 



^ Cf. the (not very good) fig. 6 by Meyer and Moebius. 



