24 LIVERPOOL BIOLOGICAL SOCIETY. 
Roule, in 1884, in an elaborate work on the Simple 
Ascidians of the coasts of Provence,* discusses the above 
theories, and comes to the conclusion that the dorsal 
tubercle is not a sense-organ, and that the hypophysial 
gland is not a renal organ, but merely a gland for the 
production of the mucus which is spread over the front of 
the branchial sac to entangle food particles contained in 
the passing water. 
This theory is open to the objection that it does not 
account for the varied and highly complicated condition 
of the dorsal tubercle in most Ascidians. On the other 
hand, the absense of a direct and conspicuous nerve 
supply tells against the view that the tubercle is at the 
present time a functional sense-organ. Possibly that was 
its original function, but was lost after the connection 
with the duct from the gland became established, and, as 
a result, the nervous connection with the ganglion has 
since disappeared. Further investigations, however, are 
required to clear up this matter. Embryology as yet has 
thrown no light upon the subject. 
Recent investigations, then, tend to establish that the 
pineal gland and the pituitary body of the vertebrate 
brain are both of them the remains of organs which 
reached the surface of the head in the ancestral Chordata 
(see hypothetical form represented on PI. II., fig. 4)—the 
pineal in the form of a median dorsal organ of sight, and 
the pituitary possibly also as a sense-organ placed on the 
front of the head close to the mouth opening. 
* Ann. du Musée de Marseille, Zool., t. ii., Mém. no. 1. 
