74 ROYAL SOCIETY OF CANADA 
tions Carlgren suggests. In none of the examples of Rh. davisii collected 
at St. Andrews were there any visible verrucæ, either in the living or 
the preserved condition, but, on the other hand, examples of crassicornis 
from Puget Sound possess well developed verrucæ, to which small 
particles of gravel and shells adhere, and both these forms, according to 
Carlgren’s classification, should be referred to his genus Rhodactinia. 
Furthermore, it may be pointed out, that more than one author, Teale 
(1837), and Lütken (1861), for example, describe the verrucæ as 
varying in distinctness from time to time in the same individual, and 
that Carlgren himself refers to the genus Tealia a species, 7’. lofotensis, 
in which the verruce are so small that he at one time proposed to term 
it Urticina crassicornis forma levis (see Appellôf, 1900). It would 
seem, then, that the verruce afford no,satisfactory basis for distinguish- 
ing the two genera. 
A similar variability obtains in the longitudinal musculature of the 
tentacles. In examples from Puget Sound, and in one of the specimens 
from St. Andrews this musculature was entirely mesoglceal; in a second 
example from St. Andrews it was partly mesoglœal and partly ecto- 
dermal, and this is the condition described by Carlgren for 7’. lofotensis. 
Further, in the Puget Sound specimens the first two cycles of mesente- 
ries were sterile, a condition that would assign the forms to the genus 
Tealia, and this is also true of the St. Andrews specimen examined. As 
to whether the ova are retained within the ccelenteron during develop- 
ment in the American forms I have no personal knowledge, but Verrill 
(1864) states that Rh. davisii “discharges young of various sizes, and 
probably eggs also.” 
It seems clear, therefore, that in all the features assigned as dis- 
tinctive between the two genera recognized by Carlgren great variation 
occurs, and it would seem more accurate and convenient to look upon 
crassicornis as a widely distributed and somewhat variable species, 
rather than to divide it into distinct species, to say nothing of genera, 
whose definitions are too uncertain for relatively exact application. 
There may be, it is true, varietal peculiarities associated with the wide 
distribution, our west and east coast forms, for instance being at first 
sight very different in appearance, but I would not go further than to 
recognize them as possible races or varieties of the same species. 
Assuming, then, the unity of the species, there remains for consider- 
ation its proper name, and first with regard to the generic term. Up to 
1832, the species was referred to the genus Actinia, but in that year 
Ehrenberg divided that genus into several subgenera characterized by 
the equality or inequality of the tentacles, and the Act. isacmza he 
further divided into two sections which he named Discosoma and Urti- 
cina.® In the Urticina section the first species named is A. crassicornis 
