230 CHAS. L. WALTON. 



Hlity results from the different environment. It seems probable that 

 these organs are defensive (possibly offensive), and they certainly 

 contain many nematocysts, and their colour may be interpreted as 

 "warning." These organs are not plainly visible during complete 

 expansion, and not at all during retraction ; but when the anemone is 

 startled (if the blue basal line be touched, etc.) the tentacles are 

 partially withdrawn and the acrorhagi are then exposed and show 

 very plainly. A good deal has been written respecting these organs, 

 .and they have been referred to as eyes, special sense organs, etc. 



Messrs. G. Y. and A. F. Dixon in treating of this species, besides 

 mentioning irregularities of form and colour, say : " Each spherule 

 •contains a prolongation of the general body cavity, and can con- 

 .sequently be dilated at will," and they relate that a specimen dilated 

 greatly, and brought the spherules into contact with the glass of the 

 aquarium. When the organs contracted and withdrew, portions 

 remained forming conspicuous blue spots. Examination of these 

 ;showed numerous spindle-shaped cells, as described by Hollard (Ann. 

 de Sci. Nat. Zool., 3 ser., vol. xv., p. 272), and they conclude that the 

 .anemone had evidently engaged in an attempt to sting the glass front. 



I have never been able to demonstrate the discharge of nematocysts 

 from these organs, but have on more than one occasion observed great 

 -distention of the acrorhagi, so that the increased weight caused the 

 .anemone to bend over on one side, and so bring the projecting organs 

 into contact with objects which happened to be in close proximity. 



The pale specimens with few acrorhagi are frequently as large as 

 those darker ones with many, so that the increase must be either 

 -due to more light, or, owing to inhabiting more exposed positions, 

 there is greater need of protection by increased batteries of nemato- 

 -cysts. 



Sagartia miniata (Gosse) is under most conditions to be classed 

 amongst species whose colouration is of a " warning " nature, and is 

 amply provided with acontia which are very freely emitted. As a rule 

 they form very conspicuous objects on the sides of rocky pools. I 

 have examined hundreds of specimens from the North Sea, which 

 though showing many minor variations were all of the same type 

 even when from a depth of 40 to 47 fathoms, where the bottom was 

 black mud (see Actiniae of the s.s. Huxley, 1907); but Mr. L. K. Craw- 

 shay showed me living specimens from the Bay of Biscay deep water 

 in which the colouration was dull, the scarlet being absent, probably 

 owing to lack of light. This variety entirely lacks the bright colours 

 of the typical form. I recently found a specimen which harmonised 

 -with its surroundings in a remarkable manner. It was affixed to the 



