Stephenson — Certain Actiniaria collected off Ireland. 107 



useful. But another way which is sometimes very valuable for nematocysts 

 is to stain first for a very short time (not more than half a minute) with 

 methylen blue; then wash quickly in water, stain for an equally short time 

 with piero-saiirefuchsin, dehydrate, and clear as rapidly as possible. 1 have 

 only actually used this method once, but it then stained thick-walled sting- 

 cells deep blue, spirocysts vivid purple, and the protoplasm pale purple— the 

 spirocysts being much more clearly visible than otherwise.' 



"With regard to the Plates, I have drawn them as far as possible in pure 

 black and white to avoid expense ; and it must consequently be remembered 

 that this gives to many of the illustrated structures a harder aud more definite 

 appearance than they actually have in sections ; and this applies, of course, 

 in lesser degree to whole specimens. 



Finally, I wish to offer my most hearty thanks to Prof. G. C. Bourne, F.E.S., 

 Prof. H. J. Fleure, D.Sc, Dr. E. J. Allen, F.E.S., and Mr. 0. L. Walton, M.Sc,, 

 for willing help concerning various points, which they have given me during 

 the course of my work. I should say that Mr. "Walton had provisionally 

 identified some of the specimens before I made a start with them, and I am 

 pleased to acknowledge the help which this gave me. 



DESCRIPTION OF SPECIES. 

 Sub-order ACTINIARIA. 



I. AOTINIINA M. Edw. 

 Family ILYANTHIDAE Gosse. 



Actiniina with the aboral extremity of the body rounded, so that there is 

 no pedal disc. No acontia. 



I am using the term Ilyanthidae here, as before, as a general heading, 

 with certain sub-divisions, but hope to enter into the relationships of the 

 contained forms in another place. 



Sub-family HALCAMPOMORPHINAE Carlgren. 

 Ilyanthidae with the sphincter endodermal or absent. 



Group A. PEACHEAE. 



Halcampomorphinae with 10 pairs of mesenteries only, of which either 

 i mly 6 pairs or all the 10 pairs may be perfect. Conchula present or absent. 



Peachia Gosse, 1855. 

 Siphonactinia, Dan. and Kor. 1856. 



Peachiae with only 6 pairs of perfect mesenteries, and with a conchula 



aud 20 tentacles, which are not knobbed. 



[P2] 



