THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 6. JUNE 1858. 



XXXVI. — Anatomical Observations on a new form of Compound 

 Tunicata. By Joiix Denis Macdonald, Assistant Surgeon 

 of H.M.S. ' Herald.' 



WuiLE cruising in Bass's Strait, two beautiful specimens of a 

 conii)ound Tunicary, whose pyriform zooids exhibited much of 

 the characteristic organization of Boltenia and Cystingea, were 

 taken in the trawl from a depth of 10—12 fathoms. The zooids, 

 each measuring about half an inch in length, were clustered 

 round the upper or free part of a long cylindrical stem, f ths of 

 an inch in diameter ; and, as they were all apjiended to this com- 

 mon peduncle by distinct pedicles, the whole formed an elegant 

 raceme composed of a transparent, colourless, and delicate car- 

 tilaginous basis, the equivalent of the test in simple Tunicata. 



It will be convenient to describe this interesting form as pre- 

 serving what we may assume to be its natural position, viz. with 

 the stem erect, the long axis of the zooids more or less hori- 

 zontal, and the branchial opening turned upwards; it being 

 understood that the latter and the cloaeal aperture hold the 

 same relations that obtain in Boltenia and Cystingea, the bran- 

 chial orifice being proximal or nearer the pedicle, and the cloaeal, 

 distal or subtermiual. 



The test is smooth externally, and so transparent that its 

 delicate cells are not very readily detected, though the equable 

 distribution of the bright and rounded nuclei is at once apparent. 

 There are no "pallio-vascular"* processes or ramitications in 

 the pi-oper test of the zooids ; but a tubular prolongation of the 

 mantle, running through the pedicle of each, connects it with a 



* I era])loy this term for convenience, not being aware that anv (hstinc- 

 tive name has been given to the structures to which it is apphed in the 

 text. 



Ann. ^ May. N. Hist. Ser. 3. To/, i. 26 



