AOTINLM AND OTHER ACTINOID POLYPS. 39 



mouth and the pores of the body that serve for the escape of 

 water on the contraction of the animal. 



Actinias have usually no gills or branchice for the aeration 

 of the blood, the whole surface of the body being ordinarily 

 sufficiently soft and delicate to serve in this function. Some spe- 

 cies live half buried in the sand, and, as this in large species 

 would prevent the skin of the sides from aiding in respiration, 

 there are sometimes very much lobed and crimpled organs, 

 attached to, or alongside of, the tentacles, which give the an- 

 imal-flower much greater beauty, and at the same time increase 

 the extent of surface for the purposes of aeration ; they are 

 set down as branchial by Prof. Verrill. 



In one tribe of polyps closely related to the Actiniae, the 

 Zoanthids, in which the outer skin is usually somewhat cor- 

 riaceous, or is filled with grains of sand, there are narrow gills 

 arranged vertically, one either side of the larger radiating sep- 

 ta, figures of which are given in the author's Zoophyte Atlas. 



As to senses, Actiniae, or the best of them, are not quite 

 as low as was once supposed. For, besides the general sense 

 of feeling, some of them have a series of eyes, placed like a neck- 

 lace around the body, just outside of the tentacles. The yel- 

 low prominences in this position on the larger figures in the 

 frontispiece are these eyes. They have crystalline lenses, and 

 a short optic nerve. Yet Actiniae are not known to have a 

 proper nervous system : their optic nerves, where they exist, 

 are apparently isolated, and not connected' with a nervous 

 ring such as exists in the higher Radiate animals. 



Reproduction is carried forward both by ova and by buds, 

 though the latter method is mostly confined to the coral-mak- 

 ing polyps. 



The ovarian and spermatic functions belong to the radia- 

 ting septa in the interior cavity of the Actinia, and to the part 



