418 THE CANADIAN NATURALIST. [DeC. 



Agassiz Rhodiictinia Davisii, and which is tlie most common 

 species on the north shore of the Gulf and River St. Lawrence, 

 may be noticed here. It is probably a variety of Actinia crassi- 

 cor?u's of the British coast. Externally, when expanded, it pre- 

 sents a cylindrical body attached at the lower extremity to a rock 

 or stone, and at the upper having a crown of thick worm-like ten- 

 tacles arranged in several rows, in the centre of which is the 

 mouth. The external surface of the body, the tentacles and disc 

 are often gaily coloured in shades of purple, crimson, and flesh 

 colour, though diff"erent individuals differ very much among them- 

 selves in this respect, and also in the smoothness or tuberculated 

 character of the body. When fully expanded, the animal has the 

 appearance of an aster or other stellate flower. When irritated 

 or alarmed it withdraws its tentacles, contracts the body wall over 

 the disc, and assumes the form of a flattened cone. Its food con- 

 sists of such small animals as may be attracted by its gay colours, 

 or may accidentally come within reach of its tentacles. Tu enable 

 it to seize these it has in the substance of the tentacles an appa- 

 ratus of extensile and retractile thread-cells, by means of which 

 it can hold with some tenacity any object which touches the ten- 

 tacles, and can also exert a benumbing influence tending to para- 

 lyze and subdue the resistance of its prey. The specimens figured 

 (Figs. 43 and 47,) were dredged in Gasp^, and referred to a new 

 species, R. nitida, but may possibly be a variety of the above. — 

 Another variety, found in the River St. Lawrence, is permanently 

 tuberculated, and cannot be distinguished from A. (Urtichiia') 

 crassicornis, as ordinarily seen in Great liritain. 



Fig. 47 



Actinia (Urtidula) CRASSicoii.MS, contrat'ted, and suuiller individual 

 expanded. 



A larger and often more beautiful representative of the Acti- 

 noids is the Metridium marginatum, a species closely allied to 

 the Actinia dianthus of Great Britain. It is found in great per- 



