192 Southern Cross. 



resemble those figured in the Catalogue of the Tunicata in the 

 Australian Museum. 



The species shows considerable variation in external form and 

 also in internal structure. But the present specimens, although 

 varying in the proportions of stalk to head,. and in the amount of 

 corrugation of the surface, are all clearly members of the species and 

 agree in essential characters, such as the peculiarly convoluted dorsal 

 tubercle. There is some variation shown in the branchial sac, not 

 only in different individuals, but also in different regions of the same 

 sac. Some parts are like the specimen figured in the ' Challenger ' 

 Eeport (PI. VIL, fig. 7), with many (six to nine or so) stigmata in 

 each mesh. Other parts are much more solid (see PL XIX., fig. 1) 

 and contain only two or four circular stigmata in a mesh, and some- 

 times only one large opening (figs. 1 and 2 show two such irregular 

 parts of the same branchial sac). The latter condition recalls the 

 branchial sac of the allied abyssal genus Culcolus, and suggests the 

 possibility that the condition in the latter may be a secondary one 

 due to the fusion of stigmata, or possibly to the arrest of subdivision 

 of stigmata, so that as the sac grows older stigmata may become 

 much enlarged. In all cases the vessels of the branchial sac contain 

 spicules as figured in the Australian Museum Catalogue (PL Cyn. I., 

 fig. 2). 



The test is also crowded with short knobbed spicules like those 

 of Alcyonaria. In some places the test is mottled on the surface 

 with circular black spots, which are seen in sections to be due to 

 spherical masses of yellow-brown pigment granules. It is not 

 improbable that these pigmented masses are the remains of parasitic 

 algae. 



Sub-Family STYELINAE. 



Styela lactea. (Plate XIX., figs. 3-8.) 



(See ' Challenger' Rep., Pt. I., p. 150.) 



Half-a-dozen specimens of this species were found " washed up on 

 the beach" at Cape Adare on 6th April, 1899. The largest measures 

 8-5 cm. in antero-posterior extent by 5-5 cm. dorso-ventrally, and 

 the smallest shows 3 cm. and 2 cm. for the same two dimensions. 

 These specimens are considerably larger than the ' Challcwjer ' 

 specimens obtained at Kerguelen Island, the largest of which 

 measured 4*5 cm. in length and 3*5 cm. in breadth. 



The Cape Adare specimens show a marked posterior pad-like 

 thickening, upon which the animal evidently rested (see PL XIX., 



