1912] Ritter: The Marine Biological Station of San Diego 197 
But the programme of the station specifically in hand, that 
of studying the occurrence and ecology of the pelagic fauna and 
flora, by no means comprehends all that has been accomplished 
in the way of answering those larger questions of the living 
world that are particularly approachable through the life of this 
locality. 
(6) Morphological and Physiological Studies 
Torrey and Martin (1906) describe an instance of sex differ- 
ences among hydroids that amounts almost to secondary sexual 
characters even so far down in the animal seale as this. The 
highly modified branches, called corbulae, which carry the sex 
elements in the Rlumularian genus Aglaophenia are quite dis- 
tinetly different in the species examined. 
Dr. Watson’s extensive study (Watson, 1911) of the fish 
parasite Gyrocotyle, though carried on largely in the zoological 
department of the University of California, Berkeley, was based 
on material much of which was collected at the station, and some 
of the work was done here. The investigation -was undertaken 
primarily with the hope of settling the debated question of which 
end of this animal should be regarded as the head. Much of 
the creature’s structure, both gross and microscopic, was ex- 
amined and the movements of the living animal were studied 
to a considerable extent in their bearing on the main question. 
The conclusion is that the end bearing the acetabulum or adhesive 
cup is the true anterior end. This is based partly on the faet 
that the animal crawls, so far as it crawls at all, with this end 
foremost; and partly on morphological evidence, particularly 
in connection with the nervous system. Another point, seem- 
ingly not specially contemplated at the beginning of the study, 
turned out to be one of the most significant of all, namely, that 
of the bearing of the conclusions above indicated on the question 
of which is the anterior or ‘‘head’’ end of the tapeworm. Cogent. 
reasons are brought forward in support of the view that the 
attached end, or scolex of this latter parasite, which is commonly 
called the head, is really the tail end, the ‘‘head”’ having been 
lost. A rather interesting detail is the fact that there is “no 
trace in any tissue of the body of an epithelial layer of cells.’’ 
