92 PROFESSOR W. A. HERDMAN ON THE 



of the species in my report upon the Tunicata of the Discovery Expedition."" The 

 Discovery obtained in all five specimens from the east end of the Barrier and the 

 neighbourhood of the winter quarters in MMurdo Bay, in 1 0-20 fathoms. 



The more abundant material obtained by the Scotia gives us still further informa- 

 tion in regard to the characteristics and variation of the species. Some of the Scotia 

 specimens, measuring up to 11 x 7 x 5 cm., are the largest yet obtained ; and some of 

 them show a short peduncle at the place of attachment, a feature not previously 

 observed. The characteristic spines on the test reach in some of these larger specimens 

 to a length of 21 mm. and a breadth of about 1 rnm. at the base. In some of these 

 specimens the musculature of the mantle is remarkably strong, and consists externally of 

 circular siphonal sphincters, beyond which is an oval sphincter, of numerous fibres, 

 enclosing both siphons, while more internally radial muscles formed of exceedingly 

 stout and strong fibres run outwards from the base of the siphons. Connective tissue 

 permeated by fine fibres covers and unites all these various muscle bundles. 



Of the six folds on each side of the branchial sac, the largest is the one next to the 

 dorsal lamina on each side, and the smallest is generally the third counting from the 

 dorsal to the ventral edge. The transverse vessels are of four different sizes, and the 

 stigmata are from nine to twelve in a mesh. One dorsal tubercle examined measured 

 4'8 mm. from side to side and 3 "2 mm. antero-posteriorly. 



The nerve ganglion is extraordinarily narrow and elongated, and may reach 9 '5 mm. 

 in length, with two nerves diverging from each end which can be traced with the eye 

 round the sphincters of both siphons. The subueural gland is in the form of a thin 

 layer over the ganglion. 



A strong band of muscle fibres lies under the dorsal lamina and extends from the 

 mantle into the wall of the branchial sac near the posterior end of the nerve ganglion. 



Two of the specimens had Amphipods in the branchial sac. The specimens were 

 obtained as follows : 



I. Station 325,t 9-10 fathoms, Scotia Bay, South Orkneys, July 1903. 



(1 ) 9 x G x G cm. (on a short peduncle). 



(2) 9'5 x 6'5 x 3 cm. (very short peduncle). 



(3) 8x5-5x4 cm. 



II. Station 325, 9-10 fathoms, June 1903 ; temp. 29" F. 



(1) 4 x 4'5 x 2'5 cm. (test only). 



(2) 8 x 5'5 x 4 cm. (with a smaller one attached). 



III. Station 325, 9-10 fathoms, August 1903 ; temp. 29 F. 



(1) G x 5 x 4'5 crn. (also four empty tests). 



IV. Station 325, 9-10 fathoms, May 1903 ; temp, about 28 F. 



(1) 7 '4 x 5 x 5 cm. 



(2) G x 4 x 4 cm. (also four empty tests). 



* Report National Antarctic Exped. : Nat. Hist., vol. v., "Tunicata," London, 1910. 

 + The whole of Scotia Bay is termed Station 325 ; consequently, depths vary. 



(ROY. soc. EDIN. TRANS., VOL. XLVIIL, 310.) 



