g^iO Dr Coldstream's Additions to the 



The reddish lines, said to mark the orifices, do not always exist. 

 Inner tunic very soft, transparent, and furnished with three or 

 four longitudinal muscular bands. Branchial membrane dusky 

 green, with a tinge of blue. It has been doubted (Cuvier, 

 Mem. sur les Ascid. 7.), whether the Ascidice, in contracting 

 their tunics, expel the water through their anal as well as 

 through their branchial orifices. I have distinctly seen this 

 species, as well as others (in particular the A. intestinalis), pro- 

 pel currents of water through both orifices, at every contraction 

 of the tunics, that from the anal orifice being almost as strong 

 as the one from the mouth of the branchial sac. When the A. 

 prunum is in a state of rest, a slow and uniform current can be 

 perceived flowing inwards through the opening into the branchial 

 cavity, but none can be detected entering the anal orifice. The 

 voluntary contractions for the expulsion of the inspired water, 

 take place at irregular intervals of time ; but, for the most part, 

 not more frequently than once in a minute. The steady flow 

 of the inward current through the branchial opening, seems to 

 strengthen Cuvier's supposition with regard to the mechanism 

 of respiration in the Ascidice, (Mem. 17.) 



This species occurs sparingly in the Firth of Clyde, adhering 

 to the under surfaces of slate boulders *. 



Ascidia (Lamarck) rugosa, C — General form somewhat coni- 

 cal, compressed ; length upwards of two inches ; surface of outer 

 tunic greenish, irregularly wrinkled, rugose, harsh ; substance 

 almost cartilaginous, near the base very thick ; orifices approxi- 

 mate, large, compressed, slit-like ; branchial one terminal. The 

 prolongations of the inner tunic, which unite it to the outer one, 

 are attached nearly half an inch within each of the orifices of the 

 latter ; inner tunic whitish, transparent ; branchial tube fur- 

 nished with two layers of muscular fibres ; external, transverse ; 

 internal, longitudinal ; orifices studded with minute red spots ar- 

 ranged irregularly ; branchial cavity, extending the whole length 

 of the inner tunic, straight ; branchial membrane greyish, reticu- 

 lated. A fold, projecting into the branchial cavity, and conti- 

 nuous with the membrane lining its walls, is attached along its 



• Professor Jameson, in his paper on Vermes, enumerates the Ascidia 

 pr'imim among the marine animals of the Firth of Forth.— FJrfe IVern. Mem, 



