KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63- N:0 2. 35 



atrial tentacles are sparingly arranged in one row. The dorsal lamina is plain- 

 edged and not very broad. The dorsal tubercle is large; the opening is C-shaped 

 and the open interval is directed to the left. (Cf. Pl. 2, fig. 31.) 



The branchial sac has rudimentary folds vvith a varying number of internal 

 longitudinal vessels. The average number may be as follows: 



right side: dorsal lamina — 4 to 7 — 1 to 2 — 3 to 5 — 1 to 2 — endostyle; 

 left side: » » —3 to 5—1 to 2—3 to 5—1 to 2— 



On the interspaces between the folds, no well-developed intermediate vessels 

 have been observed; only rudiments of two such vessels ha ve been found in the upper 

 part of the branchial sac of a few specimens. 



The external structure of the alimentary canal is shown from fig. 30. The 

 oesophagus is rather long. The stomach is short and straight, well marked off from 

 the oesophagus and the intestine. It is provided with about 15 longitudinal folds 

 which issue from a raphe. The intestine forms rather a short, rounded loop. The 

 rectum arises along almost right angle and the margin of the anus has 18 — 20 small 

 lobes. 



The gonads are few in number; they are usually 3 on the right side, and 2 

 or 3 on the left. On the left side they are sometimes 4 in number, in which case 

 one or two are rudimentary (Pl. 2, fig. 29). They are short and polycarp-like, ar- 

 ranged in a row on each side of the body-wall. The ovary is situated on the inner 

 side of the gonad and the testis on the outer side. When well-developed, part of 

 the testis might be visible even on the inner free side of the gonad. (Cf. Pl. 2, 

 fig. 29.) As appears from fig. 32 the male glands are only six in number; they 

 might be more or less lobed. The väsa efferentia are as many. The vas deferens 

 opens beside the aperture of the oviduct. Like the sperm-duct the oviduct is very 

 short. The openings of the gonads are directed towards the atrial siphon. 



Remarks on the (ienus Cnemidocarpa. 



The species included in this genus are characterized by a few to many elon- 

 gated, hermaphrodite gonads, regularly arranged on each side of the body. The 

 atrial tentacles are placed in a single row at the base of the velum. As regards the 

 structure of the branchial sac two groups are to be distinguished: one is distinguished 

 by well developed branchial folds, in the other the branchial folds are more or 

 less reduced and substituted by groups of longitudinal vessels. In the collections 

 examined only one species is to be referred to the first-mentioned group: C. fin- 

 markiensis. The second group comprises C. morte?iseni, C. rhizopus, C. mollispina, 

 C. cirrata and C. mollis Stimpson. The latter has been reported from the east coast 

 of North America under different names (Glandula mollis, G. arenicola, Tethyum 

 arenicolum) and is probably synonymous with Styela vestita Stänger of the British 

 coast. This group may conveniently be named the rhizopus group, the forms here 

 treated of agreeing as to principal characters with the species rhizopus. If we com- 



