AUGUSTA ÄRNBÄCK-CHRISTIE-LINDE, NORTHERN AND ARCTIC INVERTEBRATES. 



B. Testis not separated from the ovary, both forming a cylindrical body, 

 the testis being placed on its outer side, and the ovary on its inner 

 side. 



1 . Gonad one on each side of the body, elongated, U-shaped. Atrial 

 tentacles scattered över the velum. Ypsilocarpa n. gen. 



2. Gonads few to many on each side of the body, elongated, straight 

 or tortuous, generally arranged in a single row on the inner side 

 of the mantle. Atrial tentacles in a single row at the base of the 

 velum. Cnemidocarpa Huntsman 1912. 



3. Gonads many, small and short »polycarps», generally diffusely 

 scattered on the inner side of the mantle. Atrial tentacles arranged 

 in a single row. Branchial folds well developed. 



Polycarpa Heller 1877. 



II. Reproductive organs only on the right side of the body. Vasa efferentia 



typically opening by many very short ducts, placed on the inner free 



side of the gonad. 1 Dendrodoa Mac Leay 1824. 



Styela Fleming 1822. 



I. One gonad on each side of the body. 



A. Stalked forms. Reproductive organs retort-shaped. ? 



1. Stomach vertically placed. Test gelatinous. S. gelatinosa Tkaustedt 1887. 



2. Stomach horizontally placed. Test opaque, tough, warty. S. doliolum Bjerkan 1905. 



B. Stalkless forms. 



a. Dorsal lamina plain-edged. 



1. Ovaries sinuousty curved, the right one sometimes bent to form 

 an angle. The male glands form compact, bean-shaped masses, 

 placed along both sides of the ovary. Opening of the dorsal 

 tubercle horse-shoe-shaped, one horn usually inrolled. Test 

 usually strongly wrinkled; a pyramid-like projection — »the 

 horn» — is often present between the apertures. Body usually 

 elongated. S. rustica Linné 1767. Pl. 1, figs. 1—2. 



2. Both ovaries sharply bent to form an angle. Male glands in the 

 form of dusters, arranged at the proximal end and usually 

 along one side, sometimes along both sides, of the ovary. Open- 

 ing of the dorsal tubercle almost ring-shaped. Test often pro- 

 vided with minute wart-like projections. Body usually dorso- 

 ventrally compressed. 8. loveni Särs 1851. Pl. 1, figs. 3 — 4. 



b. Dorsal lamina with long pointed teeth. A rudimentary fifth fold is present on the right 

 side. S. bathybia Bonnevie 189fi. 



1 In the description of Dendrodoa uniplicata Bonnevie nothing is mentioned about the strueture of the 

 ducts of the reproductive organs nor about their openings. 



2 It seems most probable that a re-examination of the species gelatinosa and doliolum will prove them 

 to be identical forms. 



