168 PROF, W. A. HEEDMAX ON FUNICULINA QUADRANGULARIS 



character that may enable the Hebridean to be separated from Savigny's 

 species with " slender, pointed '^ papillae. But, as a matter of fact, neither 

 the southern nor the northern form has any papillae at all in the branchial 

 sac, as was explained * in my paper in 1891. As I stated then, the " hooked 

 fleshy tubercles" ( = papill?e) of Forbes and Goodsir's description can bo 

 quite satisfactorily accounted for by the corrugation of the internal longi- 

 tudinal bars, the thick prominent connecting ducts which seem to project on 

 each side where they join the bars, and the imperfect condition of the bars 

 in some parts of the sac. When a branchial sac is first opened, in the case 

 of most ascidiozooids, and is examined in water under a low power of the 

 microscope, the appearance of large papillae at the angles of the meshes is so 

 distinct that it is difficult to realise, until the specimen has been stained^ 

 mounted._, and examined in detail with a high power, that only connecting- 

 ducts and more or less irregular bars are present. There is no difficulty in 

 understanding how it is that some previous investigators have fallen into 

 the error of supposing that they saw large papillae. Figs. 4 to 16 on 

 PI. 14 illustrate these remarks. Figs. 5, 6, & 16 show corrugated 

 internal bars forming projections, but without any true papillae ; figs. 4, 12, 

 13, & 14 show connecting ducts which have not grown together to form 

 bars, and so give a deceptive appearance of being large pa])illac. 



In regard to the supposed difference between the two forms in the number 

 of stigmata in a mesh, the range of variation is great (see figs. 10 to 15) and 

 is much the same in all the specimens I have examined, as is shown by the 

 following note : — 



Naples (1912) specimen has 2-3 stigmata m a mesh. 

 Mull (1885) „ 1-4 



'Runa' (1912) „ 1-3 



Plymouth „ 1-3 „ 



Probably some parts of each of the branchial sacs could be found showing 

 the four stigmata in a mesh described by Savigny, and certainly many parts 

 show the single stigmata referred to by Forbes and Goodsir. The stigmata 

 are found to differ also very greatly in size and shape in different parts of 

 the same sac (fig. 9). 



The distinctions depending upon lines of white pigmentation on the 

 ascidiozooids referred to by Forbes and Goodsir, Giard, Lahille, and others 

 are so slight and so unreliable that in the absence of any real structural 

 differences they need not be considered. Lahille regards them as at most 

 serving to separate the type and two varieties which he proposes to call : — 

 (Type) D. violacea, Sav. — (Mediterranean.) 

 (Variety 1) 1). hehridica-violacea, Forb. — (Hebridean seas.) 

 (\'^ariety 2) D. intacta-violacea, Lab. — (Banyuls.) 



* And was also shown by Laliille in the case of the Mediterranean form (Eecher. sur 

 les Tuniciers, Toulouse, 1890). 



