THE ACTINIANS OF PORTO RICO. 
325 
E. van Beneden (1897) in his great work, “Les Anthozoaires de la Plankton- 
Expedition,” has come to the conclusion that the Ceriantharia should be entirely 
removed from among the Actinians, as generally understood, and united with the 
Antipatharia to form a single group, Ceriantipatharia. In a similar manner he 
unites the Actiniaria (restr.) with the Madreporaria under the term llexactiniaria. 
The evidence for the relationship of the Ceriantharia and Antipatharia is mainly 
embryological, and concerns the mode of origin of the first pairs of mesenteries and 
their associated chambers. 
The character of greatest importance among the Ceriantharia is the appearance 
of the metacnemes in bilateral pairs at only one region of the polyp. Since the 
publication of van Beneden’s work I have found that a somewhat similar method of 
mesenterial increase is followed by the coral Porites (1900), the other characters of 
which undoubtedly mark it out as a Hexactiniarian. The mesenteries beyond the 
primary six pairs appear in bilateral pairs within the entocoele of either the dorsal or 
ventral pair of directives (tig. 4, plate A). This discovery must be considered as 
modifying in sonie degree the strong separation from the Actiniaria which van 
Beneden has tried to establish for the Ceriantharia. 
The arrangement proposed by van Beneden (p. 182) is as follows: 
/a >anthactiniaria 
Cnidaria. 
Anthozoa=Scyphozoa 
Ilydrozoa. 
Octactiniaria. 
■Scyphactiniaria . 
fZoanthiniaria [=Zoan there.] 
{ Madreporaria. 
Actiniaria. 
{ Ceriantharia. 
Antipatharia. 
Scyphomedusa. 
Rugosa. 
As the report was approaching completion 1 received the valuable paper “ Osta- 
frikanische Actinien,” 1900a, by Dr. Oskar Carlgren. As a contribution to the 
systematic study of the Actiniae the work is of great importance, and calls for lengthy 
notice, especially as many of the present West Indian species are therein referred to. 
The author introduces a classification of the Actiniaria ( Ilexactinue ) toward which 
he has been working for some time, the fundamental features of which are different 
from those hitherto accepted. In their systematic studies the earlier actinologists 
had to content themselves mainly with external characters. Gosse’s “British Sea- 
Anemones” and Andres’ “ Le Attinie” are classic examples of this type. After the 
introduction by the brothers Hertwig (1879, 1882), about twenty years ago, of ana- 
tomical and histological methods of study, in which the} 7 were followed bv Haddon, 
McMurrich, and others, the classification of the Actiniaria was founded upon the com- 
bination of external and anatomical characters. Among the former were included the 
arrangement and number of the tentacles, the nature of the column-wall, etc., and 
among the anatomical characters the arrangement of the mesenteries, the musculature, 
and the gonads. Carlgren now goes still deeper and, for the primary subdivisions, 
subordinates these more obvious features to histological details, the principal of which 
