EOLIS. 



It receives three large venous trunks, two of which pass from the skin backwards to the 

 sides of the auricle (fig. 1 1, I), and the third joins it from behind on the median line. 

 These three trunks result from the union of veins from the skin. Two small branches also 

 unite with the posterior trunk from below. We have not been able to trace satisfactorily the 

 means by which the blood is conveyed from the arteries to the veins, but there can be 

 little doubt that, in this respect, Eolis resembles the other nudibranchs. 



The respiratory function appears to be partially specialised in the dorsal papillae, which, 

 usually exposing a large surface, are covered with strong and vigorous vibritile cilia ; but as 

 the blood, in its return to the heart, appears to pass almost entirely through the skin, which is 

 thin and delicate, and also covered with cilia, there can be little doubt that the whole surface of 

 the body assists in its aeration. The cilia of the dorsal tentacles, which are also very strong, 

 we consider to be connected with the sense of smelling. 



The central part of the nervous system consists of a series of ganglions and connecting 

 cords (fig. 3), placed round the commencement of the oesophagus. Four large principal 

 ganglions rest on the buccal mass immediately in front of the oesophagus : the two next the 

 median line are much the larger, and are of an irregular ovate form ; the other two are 

 circular, and are closely attached to the outer sides of the central pair. These ganglions are 

 connected together by three collars that pass under the oesophagus. The inner one is much 

 shorter and thicker than the other two, and passes from the posterior margins of the lateral 

 ganglions ; the two outer ones pass from the sides of the inferior surface of the central ganglions, 

 and lie nearly in contact with each other. One is much smaller than the other, and is placed 

 immediately in front of it, — this is the central collar : the larger or outer collar has two 

 small oval ganglions, which are connected together on the median line, and are usually 

 called the buccal ganglions. The first pair of nerves, which we consider olfactory, are large, 

 and rise from the anterior and upper surface of the central ganglions near the median line, 

 and passing into the bases of the dorsal tentacles, swell into two well-defined oval ganglions, 

 sending off several nerves into these organs. The second, third, fourth, and fifth pairs of 

 nerves supply the different organs of the head, in front of the buccal mass ; the sixth 

 and following pairs to the ninth go to the skin on the sides of the body and foot. All 

 these, excepting the first pair, arise from the anterior lateral margin of the central ganglions. 

 The tenth and eleventh pairs, which arise from the outer side of the lateral ganglions, supply 

 the foot and sides of the back. The twelfth pair originate from the posterior margin of the 

 central ganglions, and go to the back on each side of the median line. Besides these other 

 small nerves go to the skin from different parts of the central ganglions. The two small 

 inferior buccal ganglions give off each a large nerve, which sinking into the muscles of the 

 buccal mass, are lost there. These ganglions have attached to their inner inferior margins 

 two small ganglions, from which the stomach and oesophagus are supplied with nerves ; and 

 imbedded in the muscles of the buccal mass there is on each side another small ganglion. 

 These ganglions give off each a large nerve, which, passing within the outer and central 

 collars, is united to the former by a short but rather strong branch of communication. These 

 nerves supply the glands of the papilla?, and shortly after their origin give off minute branches 

 to the oesophagus. The central collar gives off on each side a nerve that goes to the heart 

 and generative organs. These details are taken from U. papillosa, but the nervous system 

 differs very little in other members of the genus. In some the olfactory ganglions are round 



