330 EDITH M. PRATT. 
Tn all expanded zooids grooves occur between the bases of 
the tentacles (fig. 3); they probably serve for the escape of 
waste fluid and solid matters. 
In all the genera the tentacles and pinnules are hollow 
when expanded. The surface of the latter is dotted with 
innumerable excrescences, which are due to the presence of 
batteries of cnidoblasts, each battery in Alcyonium digi- 
tatum contains some hundreds of these cells, but they are 
not usually so numerous in tropical members of the family. 
In Alcyonium, Sarcophytum, and Lobophytum the 
tentacles are fringed laterally with a single row of pinnules. 
In the genus Sclerophytum the tentacles of some species 
have one row, and others (Scl. capitale and palmatum) 
have two, while those of the genus Xenia, according to 
Ashworth, have three rows of pinnules. 
The tentacles and pinnules are apparently shortest in 
Sclerophytum and longest in Alcyonium, although it is 
extremely difficult to form an opinion as to their exact size 
from a study of preserved material alone. 
Tue Foop or tHe ALCYONARIA. 
In consequence of the many difficulties which attend the 
physiological investigation of the food supply and mode of 
nutrition in this family, little systematic work on this subject 
has hitherto been attempted. The accounts of the digestive 
processes in other groups of the ccelentrates are also very 
conflicting. 
Milne-Edwards and Wilson maintain that digestion in 
the Alcyonaria is intra-cellular, while Hickson states that 
the food is acted upon by a digestive secretion before it is 
ingested by the cells lining the digestive tract, i.e. an inter- 
cellular digestion occnrs in Alcyonaria as well as an intra- 
cellular digestion. 
In an investigation of the physiological processes of diges- 
tion it is necessary that the study of the minute anatomy of 
