168 Transdctioiis. 



Art. XVIII. — Ov the Tiinicate 8tyela coerulea (Quoij and Gaiiiiard). 



By A. J. CoTTRELL. M.A., M.Sc. (N.Z.). 



Comiminicated hy Professor Benham. 



[Bead before Ike Otago Instiiute. 3rd Decetnber. 1912.] 



This is the first of a .series of short papers dealing with the Tiinicates found 

 on the shores of New Zealand. In the earlier papers I shall deal with the 

 specimens collected by myself, and in these cases shall therefore be able to 

 give more exact information concerning the general appearance of the living 

 animal. Quoy and Gaimard described several species from our seas, a few 

 of which have not since been recorded : the species described in this article 

 is probably one of them. 



Styela coerulea (Quoy and Gaimard). 



Ascidia coendea Quoy and Gaimard. Voy. de I'Astrolabe. Zoo!., 

 iii, 1835. p. 611, pi. 91, figs. 8,9. 



This Ascidian is very common on the rocky shores of the Waitemata 

 Harbour and Hauraki Gulf. It is usually found attached to the undersides 

 of more or less flat rocks which are propped up by neighbouring rocks so as 

 to leave a space between the rock and the bottom. They may be found 

 singly, or in groups of two, three, or more, but there is no organic connec- 

 tion between the individuals of such groups. Although so common on 

 rocks, I have never been able to find it on wharf-piles. 



The external appearance corresponds very well witii Quoy aud Gai- 

 mard's account. A mature specimen when distended measures about 

 If in. long, f in. deep, and f in. wide. The body is thus long and some- 

 what oblong, rounded at the posterior end, and tapering at the anterior 

 region to end in the branchial siphon. Frequently the shape is very like 

 Quoy and Gaimard's figure, but usually it is rather more oblong. The 

 creature is attached by a considerable part of the ventral surface, and 

 usually slightly on the left side, but sometimes a little on the right. 



The branchial siphon is longer than the atrial, and is at the anterior 

 end, the atrial being situated on the dorsal surface a little behind the middle 

 point of the length. When fully distended the siphons are wide, open tubes ; 

 near its outer end each becomes gradually wider, and in this condition the 

 opening is perfectly circular, usually showing no trace of lobes. When 

 the tube is partially closed 4 lobes can be distinctly seen, but Quoy and 

 Gaimard's figure exaggerates this condition somewhat. 



The colour is a beautiful bright blue, and makes this Ascidian a 

 conspicuous object. The colouring varies much in intensity, quantity, 

 and disposition in different individuals ; generally the whole upper 

 part is a bright blue, and towards the base this gradually gives place to a 

 yellowish-cream colour. In other cases the blue colour is confined to the 

 siphons, where it is always deepest, and the rest of the body is a yellowish- 

 white or cream, often with faint tinges of blue. I have been able to collect 

 a series showing variation in colour from a deep blue to a condition in which 

 blue occurs only in small amount on the siphons. None of my specimens 

 show the double violet lines in the siphons as described by Quoy and Gai- 

 mard. but the blue colour extends down inside the siphons in the branchial 

 siphon as far as the ring of tentacles. 



The tesl is smooth in the living distended specimen, and rarely has 

 uT.uch growth of other organisms on it ; the animal has thus a clean, smooth 

 appearance. A green growth is occasionally found coveriiig part of the 



