ON THE ANATOMY AND DEVELOPMENT OF PYROSOMA = 333 
hemal and of the hypopharyngeal sinuses merely as a matter of 
convenience; in point of fact, the general blood-cavity is not 
naturally divided into distinct sinuses}. 
The wervous system consists, as in Pyrosoma atlanticum, of a single 
ganglion, of an oval shape when viewed sideways, but somewhat 
heart-shaped when seen from above, its narrower end being turned 
backwards. It is about 35th of an inch long, and is composed of a 
dark granular mass invested by a delicate structureless membrane. 
It lies between the inner and outer tunics, the former being raised, so 
as to form a slight protuberance over it. On the posterior half of 
this protuberance lies the broad lower median portion of the peri- 
pharyngeal ridge. In its anterior half, the opening of the ciliated sac 
appears. The principal nerves given off from the ganglion are the 
following. Two, a smaller internal and a larger external, pass from 
the antero-lateral parts of the ganglion, forwards towards the oral 
aperture, branching as they go. I suspect that a nerve runs up on 
each side, beneath the peripharyngeal ridge ; but I cannot make sure 
of the fact. A considerable nervous trunk is given off to the postero- 
lateral walls of the body; and, finally, two delicate trunks arise 
posteriorly, one on each side of the middle line, which run back, so as 
to have the languets between them, and passing up at the sides of the 
cesophageal aperture, are lost under the divisions of the posterior 
epipharyngeal ridge. 
In Pyrosoma atlanticuim 1 observed a mass of deep-red otoliths in 
contact with the posterior end of the ganglion (/. ¢ p. 583), but no 
1 Thave described the circulatory system of Sa/ga in similar terms to these, in my memoir 
on Sa/~a and Pyrosoma, and notwithstanding the criticism my statements have received both 
from M. Vogt and Prof. Leuckart, I must maintain their correctness. M. Vogt affirms that I 
have committed ‘a grave error’ in declaring the blood-canals of Sa/pa to be lacunce 
between the two layers of the mantle,—apparently supposing that I mean thereby the test and 
the external tunic, and forgetting my careful discrimination of test, outer tunic and inner 
tunic, at p. 585 of the memoir cited. In fact, nothing can be easier than to observe the 
entire distinctness of the inner and outer tunics in a bud or embryo of Sa/fa or Pyresoma—to 
see that the viscera and blood-canals do really lie between these tunics, and that they are 
by no means, as M. Vogt states, lodged in cavities excavated in the ‘inner mantle.’ Prof. 
Leuckart has equally mistaken my meaning when (/. ¢. p. 14) he ascribes to me a participa- 
tion in Eschricht’s opinion as to the existence of a serous sac surrounding the body of Sa/pa. 
My words in the passage cited by Prof. Leuckart are, ‘‘In very young Sa/ge, this space [the 
interval between the inner and outer tunics] is like the cavity of a serous sac.”’ Still less 
can I find in my memoir any such opinions as those ascribed to me in the note to p. 43 of 
Prof. Leuckart’s valuable memoir. While on the subject of errors, however, I am glad to 
take the opportunity of pointing out that several statements made at second-hand in my 
memoir, regarding Ascidians other than those specially described, are incorrect. The 
diagram of Pelonaza (pl. 19), again, is altogether erroneous—this Ascidian differing, as T 
have since found, in no essential respect from Cyzthia. 
