of Eclinhurgh, Session 1882-83. 147 
cubical, and then columnar ciliated cells. The cilia project into 
the cavity of the organ. 
Since the time of Savigny, the dorsal tubercle has been almost 
universally regarded as a sense organ of some kind — probably 
olfactory or gustatory, or in some way capable, as Hancock * 
suggested, of “ testing the quality of the inhaled water.” The 
reasons for this view have been — 
1. The position of the organ at the entrance of the branchial 
sac, where a sense organ would be of great apparent value. 
2. Its structure — a ciliated depression covered in part by 
columnar cells, some of which closely resemble sense cells. 
3. Its intimate relation with the ganglion, and the presence of 
a nerve arising from the anterior end of the ganglion, running 
towards the branchial aperture, close past the dorsal side of the 
tubercle, and presumably supplying it with nerves. 
In 1876, Ussow f showed that the neural gland lying below the 
ganglion was continued into a delicate duct, lined by cubical 
epithelium, which ran forwards and opened into the tubular 
posterior end of the funnel-like depression forming the dorsal 
tubercle, so that the variously-shaped slit of the tubercle was thus 
shown to be merely the aperture of the duct from the neural gland. 
Long previous to this, in 1861, Keferstein and Ehlers | had 
shown that the funnel-shaped cavity forming the dorsal tubercle 
in Doliolum derdiculatitm was continued backwards as a delicate 
duct to the base of the ganglion, but they regarded this duct 
and its anterior expansion as a prolongation from the ganglion 
itself. 
In 1881, Ch. Julin§ conhrmed Ussow’s discovery, and described 
minutely the condition of the gland, the duct, and the tubercle in 
several species of simple Ascidians. He also declared that tiiere 
was no connection between the nerve running from the ganglion to 
the branchial aperture and the tubercle, and that consequently the 
latter could not be a sense organ, and was nothing more than the 
opening of the duct. In a second pa]rer published shortly after- 
wards, Julin|l described the condition of these organs in two 
* Loc. cit. p. 335. 
t Froc. Imp. Soc. Nat. Hist., <kc., Aloscow, vol. xviii, fasc. ii. (in Kussian). 
% Zoologische Beitrdge, iii., “ Ueber die Anatomie und Entwicldung von 
Doliolum, ’ p, 61, Leipzig. § Archives de Biologic, vol. ii. p. 59. 
dl Archives dc Biologic, vol. ii. p. 211. 
