584 ' 
MR. HUXLEY ON THE ANATOMY OF SALPA AND PYROSOMA. 
rather in front of the testis (fig. 5), there could always be found more or less decided 
traces of one or more ova. 
Commonly there was a single ovum (figs. 4-6), measuring about a^th of an inch 
in diameter, with a clear germinal vesicle of ^.n inch in diameter, and a vesi- 
cular thick-walled germinal spot - feV 'ofh of inch in diameter. 
The ovum is inclosed in a strong transparent sac, continuous with a pedicle or 
gubernaciilum (fig. 6 q'), which runs to the upper and posterior part of the inner 
tunic on the left side, and there terminates in a papilla, like that of the vas deferens, 
projecting into the post-branchial cavity. 
In young specimens, when the ovum is small and the yelk pale, this gubernaculum 
frequently appears to be solid ; but in fully-grown specimens, when the ovum has its 
full size, and the yelk is darker and granulous, it presents the appearance of a wide 
tube, especially at its upper part. And here there was frequently an appearance of 
dark striae and moving granules, prompting the belief that spermatozoa had travelled 
thus far. 
In one instance (fig. 6) the sac of the ovum was empty and the gubernaculum or 
duct widely distended. The appearance of spermatozoa in the duct was here very 
strong, fig. 5. 
None of the compound ova described by Savigny were present in the specimens 
of Pyrosoma examined. 
56. The young polypes described by Savigny as existing between the fully-formed 
ones, in all stages of development, are formed by gemmation, Plate XVII. fig. 7 
A diverticulum of the dorsal sinus of the parent is formed just above the heart ; 
the extremity of this diverticulum thickens and enlarges, and assumes the form of a 
single zooid. For a long time a vascular connection is maintained between it and 
the parent, by means of a duct, in which there seemed to be traces of a longitudinal 
partition, as in the gemmiferous tube of Salpa. Ultimately the connection appears 
to cease, and the two polypes live on independently. 
It is to be remarked, that while in Salpa the ventral side of the young bud is first 
marked out, and the communication of the parent with the young is thence on the 
dorsal side of the foetus, in Pyrosoma the dorsal side is first developed, and the com- 
municating canal opens on the ventral side of the young. 
57- The ovum or ova, for there are sometimes two or three, are perceptible very 
early in the young polype produced by gemmation, and are then situated in the 
middle line posteriorly. 
58. The muscular system is best seen in a young specimen (fig. 8 h). Two very 
delicate bands encircle the inner tunic anterior to the ganglion. From the posterior 
extremity of the ganglion two strong bands arise, which diverge for about half the 
distance between the ganglion and the mouth. Here they divide into two branches, 
one of which continues the original direction, while the other meets its fellow just 
behind the mouth. The former, as it leaves the under surface to become lateral, is 
