602 
MR. HUXLEY ON DOLIOLUM AND APPENDICULARIA. 
the intestine gives attachment to three or four small caeca (.?), which appear to repre- 
sent a liver, and a system of transparent anastomosing tubules, similar to that de- 
scribed in Salpa, arises from the stomach and envelopes the intestine in a network. * 
The heart (r) lies above and in front of the mouth. In structure it resembles that 
of Salpa. There are no vessels of any kind, the blood-corpuscles making their way 
at random among the viscera. No reversal of the circulation was observed in this 
Ascidian. 
94. All the specimens examined possessed only the male generative apparatus, in the 
shape of a long tubular* testis (jw), placed on the right side and below, and opening 
posteriorly into the respiratory chamber by a papillary elevation (jo') just before the 
penultimate muscular band. 
The testis lies quite freely in the sinus, and is bathed by the blood (fig. 7 ). 
When most fully developed the testis nearly equals the body in length ; but in 
young specimens it may be not more than one-half to one-third that size. 
The young testis is a delicate sac, containing a mass of circular cells, about 3 -^^th 
of an inch in diameter, of a pale greenish colour, and flattened. 
As development proceeds, these cells assume a redder tint, and become perfect 
spermatozoa, with elongated cylindrical heads -^ gV oth of an inch in length, and 
very delicate, long filiform tails. 
95. There is a small cavity {u) resembling the ciliated fossa of the Salpce, seated 
upon the anterior face of the singular process of the ventral paries of the respi- 
ratory cavity. 
This process lies anterior to the first muscular band ; it is somewhat conical and 
excavated behind. The two lips of the excavation are thiekened and ciliated, and the 
right lip is continuous on the left side with a ciliated band, which runs up parallel 
with the first muscular band, passes over to the right side, and running down, be- 
comes eventually lost in the right portion of the base of the conical process. 
This would seem to be a rudimentary languet. A number of small granular masses 
were always to be seen attached to the inner tunic close to the posterior aperture. 
The strueture of the branchiae of this Ascidian, the position of the two orifices, 
and the structure of the testis, all indicate a position for Doliolum intermediate be- 
tween Salpa and Pyrosorna, 
Its apparent unisexuality very likely arises from the ova being developed, and 
leaving the parent in a younger state than any I examined. I have elsewhere men- 
tioned the liability to deception in Salpa from a similar cause. 
Note. — Since writing the above I have found a short notice of Appendicularia 
in Muller’s Arehiv for 1846'|~, under the name of Vexillaria Jlahellum. The de- 
* Very similar to that of Salpa cristata, described as an hepatic organ by Meten. 
i' Bericht liber einige neue Thierformen der Nordsee. 
