KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. N.O 2. 19 



and of different size. Their exact number could not be ascertained. Atrial ten- 

 tacles are present in great number. They are slender and club-shaped, scat- 

 tered över a broad velum. The dorsal lamina is broad and plain-edged. Trans- 

 versally it is strongly folded, probably owing to contraction of the tissues. Its 

 posterior part is apparently double. (Pl. 1, fig. 6.) As appears from the last-men- 

 tioned figure, the dorsal tubercle is of a very characteristic structure, differing 

 from that of other Styelae. It is prominent and of rounded form vvith two small 

 openings of semi-circular shape, the concavity of which is directed to the left. The 

 ganglion situated behind the dorsal tubercle is rather long. 



The branchial sac of the specimen at my disposal is highly contracted. It 

 is provided with four well-marked longitudinal folds on each side; the longitudinal 

 vessels of each fold are numerous, at least 12 — 15 in number. The stigmata are 

 elongate and of the usual form. On the interspaces between the folds about 8—10 

 longitudinal vessels are visible. Transverse vessels of different size cross the bran- 

 chial sac. Here and there the stigmata are crossed by slender vessels. 



In examining the alimentary canal one is struck by the development and 

 arrangement of the intestine, which is of great length and characteristically bent, 

 forming a wide, rounded loop above the stomach. The oesophagus is rather long, 

 projecting from the base of the branchial sac. The stomach is short and well marked 

 off, with about 22 longitudinal folds in its wall. Only a very small rudiment of a 

 pyloric coecum is present. (Pl. 1, fig. 7.) The condition of the rectum is noticeable; 

 it is long and sinuous and placed close to and on the inner side of the descending 

 part of the loop of the intestine. The margin of the anus has about 12 small lobes. 



The reproductive organs consist of two gonads on the right side and one 

 gonad on the left. Each gonad consists of an ovary, bordered proximally by dus- 

 ters of male glands. The ovaries are tubes of great length which are bent along a 

 sharp angle and sinuously curved. The oviducts are wide, almost inflated, the ori- 

 fices are lobed, directed towards the atrial siphon. (Pl. 1, fig. 8.) The two ovaries 

 of the right side differ in size, the one being shorter and narrower than the other. 

 In other respects they exactly agree. The ovary of the left side is in its proximal 

 part less sinuous than those of the right side. Moreover they are of the same 

 structure and the characteristic bend along a sharp angle is common to the ovaries 

 of both sides. (Pl. 1, fig. 9.) 



The want of symmetry is manifested not only in the arrangement of the ovaries 

 but also in that of the male organs. If we compare figs. 8 & 9 it will be seen that 

 the testis of the left side is much more developed than that of the right. On the 

 latter side, the dusters of male glands are few and are placed only at the proximal 

 end of the oviduct, whereas on the left side they are numerous, forming a series of 

 testicular masses, grouped along the ovary at one side and bordering the greater 

 part of its length. The väsa efferentia embrace the proximal part of the ovary and 

 unite in forming a common vas deferens, which lies on the inner free surface of the 



