134 DISCOVERY REPORTS 



Molgula bacca Herdman 

 Molgula bacca Herdman, 1910, p. 13, pi. 4, figs. 1-5. 



Occurrence. St. 175: S. Shetlands, 200 m. 



External appearance. The single specimen has a body 2-0 cm. long and stalk 0-7 cm. As in 

 Arnback's specimen from the Graham Land region the surface of the test bears very small scattered 

 tag-like processes, which are most numerous on the siphons ; they are coated with sand. The test is 

 thin and transparent, allowing the branchial folds and the gut to be seen from the outside. The shape 

 of the specimen is almost identical to those illustrated by Herdman (19 10, pi. 4, figs. 1, 2) and by 

 Arnback (1938, text-fig. 4). It seems to be constant in the species which is characterized by (1) the 

 pear-shaped body, (2) the short basal stalk, (3) the asymmetrically placed short siphons, and (4) the 

 transparent test. 



Body wall. The muscles of the body wall are slender and run almost entirely in a transverse 

 direction. They are best developed on the dorsal and ventral areas of the body, and absent from the 

 area overlying the gut. 



Table 36 



M. malvinensis M. occidentals M. pyriformis 



Dorsal tubercle opening C-shaped C-shaped Simple funnel-shaped 



Primary intestinal loop Open Nearly closed Widely open 



Secondary intestinal loop Bent to less than | circle Bent to f circle Bent to about i circle 



Left gonad Extending beyond distal bend Barely reaching distal bend of Extending to distal bend of 



of primary intestinal loop primary intestinal loop primary intestinal loop 



Distribution Antarctic and Subantarctic Warm Atlantic America and Off Buenos Aires 



tropical W. Africa 



Tentacles. Fourteen tentacles were counted, of which four were very large, occupying the dorsal, 

 ventral and mid-lateral positions. The larger tentacles are much branched and at least three times 

 pinnate. 



Dorsal tubercle. The dorsal tubercle faces obliquely to the left and rear and has the horns turned 

 inwards. 



Branchial sac. Longitudinal branchial bars are arranged as follows on the left side: dorsal 

 line 5 (12) 1 (18) 2 (18) 2 (16) 3 (13) 3 (13) 1 (12) 2 endostyle. The bars on the ventral faces of the 

 folds are stouter than those on the dorsal faces. 



I have nothing to add regarding the gut and there were no gonads in this specimen. 



Distribution. Antarctic (Graham Land region, McMurdo Bay, Kaiser Wilhelm II Land). 



Molgula setigera Arnback f. georgiana n. (Text-fig. 58A-D) 

 Diagnosis of form. Differs from the typical form of the species in (1) opening of dorsal tubercle 

 a simple longitudinal slit, (2) long bristle-like hairs of test confined to region of siphons, and (3) several 

 sperm ducts. 



Occurrence. St. 159: S. Georgia, 160 m. St. 474: S. Georgia, 199 m. 



External appearance. There are five specimens of this form, varying in length from 2-5 to 2-8 cm. 

 The shape of the body is roughly ovoid, but its outline is very irregular owing to the great amount of 

 small stones and sand sticking to the test. Only the siphons are free of this covering. The most 

 noticeable feature is a tuft of long stiff bristles round the opening of each siphon. In one of the type 

 specimens of the species described by Arnback (1938), bristles covered almost all the body except the 

 ventral side, but in the others they were sparsely arranged on the sides and dense only on the siphons. 

 In the ' Discovery ' specimens the bristles are even more strictly limited to the siphons. 



