616 Messrs. K. Elmbiist and J. Smitli Sliarpe on 



We find tliat as we go from the sliore to deep-water : 



(1) Tlie firm tough skin of tlie littoral forms disappears. 



(2) Individuals become larger. 



^ (3) 'I'he wfirt-like suckers disappear. ^ 



(4) The habit of dressing correlated with 3 also disappears. 



(5) Intensity of pigmentation and tendency to close up 



decrease. 



(6) Exposure to tidal currents is sought rather than shelter 



in crevices. 



Details confirming these conclusions may be found in. the 

 pages of Gosse (1860), Newbigin (1901), and various 

 faunistic works too numerous to list. Examination of speci- 

 mens from various localities and depths confirms Gosse's 

 view that the shore Ttalia (species coriacea, Cuvier) and 

 the deep-water Tealia (species crassicor?ns, MUller) are 

 forms of one variable species, and indicates that intermediate 

 gradations occur in habitats of intermediate depth, light- 

 conditions, etc. Some of the Clyde Tealicje are very near 

 T. iuherculata (Cocks), which Gosse (p. 217) suggests is a 

 synonym of crassicornisj but Dr. Cunningham (1890) in- 

 clined to regard them as separate. More recently Prof. 

 Gemmill (1920) has studied the development of these shore 

 and deep-water forms, and writes (p. 453) : — " On general 

 grounds I would have judged that the shore and the sub- 

 merged forms were varieties of the same species had my 

 account (see below) of the development of the mesenteries in 

 the latter agreed with that of Eauiot for the former.'"^ Later, 

 he adds, " Material is being collected for a revisal of his work 

 on this point " — viz., the order of occurrence of the primary 

 mesenteries. I tliink it is well to add here that Faurot had 

 no opportunity of examining very young specimens in which 

 the primary mesenteries and tentacles were being formed. 



Colour Significance. — The colour-schemes of littoral Tealice 

 are innumerable and extraordinarily variable, but the general 

 prevalence, particularly on the column, of heavy red, green, 

 and brown lipochromes suggests that the pigmentation has a 

 physiological function as in Actinia. Spectroscopically and in 

 certain chemical characters these red, green, and biovvn pig- 

 ments are identical with the similar pigments in Actinia 

 (McMunn, 1885), and we presume, therefore, have similar 

 functions. In the case of Actinia^ Mr. Sharpe showed '' ex- 

 perimentally by Wager's method that these red and brown 

 substances produce photo-chemical action with the release of 

 active oxygen ^^ (1920, p. 53), but in the case of Ttalia he 

 has been unable to get a definite result, owing to the vast 



