MR. HUXLEY ON DOLIOLUM AND APPENDICULARIA. 
597 
83. Mertens describes a vascular system, consisting of an aortic vessel, which runs 
forwards on the dorsal surface, and of a principal vein of a red colour, which passes 
to the ventral surface, and there divides into three branches, one of which runs for- 
wards to the “ semicylindrical body ” (ganglion ?), and the other two pass to the 
dorsal region. 
A circular canal communicating with the aortic vessel exists, he says, on each side 
of the anus, and is connected with the ventral vessel by means of a vessel, through 
which no corpuscles were seen to pass. 
I have seen nothing of this vascular system. The caudal appendage (A) is attached 
or rather inserted into the body on the dorsal surface just behind the anus. It con- 
sists of a long, apparently structureless, transparent, central axis (m), rounded at the 
attached, and pointed at the free end. This axis is enveloped in a layer (o) of longi- 
tudinal, striped, muscular fibres ; which form the chief substance, in addition to a 
layer of polygonal epithelium cells, of the broad alary expansion on each side of the 
axis. 
I did not observe the lateral canal containing air, described by Mertens. 
84. The only unequivocal generative organ I found in Appendicularia was a testis 
{p), consisting of a mass of cells developed behind and below the stomach, enlarging 
so much in full-grown specimens as to press tins completely out of place. 
In young specimens the testis is greenish, and contains nothing but small pale 
circular cells ; but in adults it assumes a deep orange red-colour, caused by presence 
of multitudes of spermatozoa, whose development from the circular cells may be 
readily traeed. 
This orange-red mass, or rather masses, for there are two in juxtaposition, is de- 
scribed by Mertens as the “ Sarnen-behalter ” or vesiculse seminales. He describes 
them as making their exit, bodily, from the animal, and then becoming diffused in 
the surrounding water. This circumstance, indeed, appears to have furnished his 
principal reason for believing these bodies to be what the name indicates. 
The spermatozoa have elongated and pointed heads about -g-Q^th of an inch in 
length, and excessively long and delicate filiform tails. 
Mertens describes as an ovary, two granulous masses, which he says lie close to 
the vesiculse seminales, and have two ducts, which unite and open into this “ ovisac.” 
This appears to me to be nothing more than the granulous greenish mass of cells 
and undeveloped spermatozoa, which exists in the testis at the same time as the 
orange-red mass of fully developed spermatozoa. 
I saw nothing of any ducts, nor do I know what the “ ovisac ” can be, unless it be 
a further development of an organ which I found in two specimens (fig. 3 </), consisting 
of two oval finely granulous masses, about ^^th of an inch in diameter, attached, one 
on each side of the middle line, to the dorsal parietes of the respiratory cavity, and 
projecting freely into it. 
Mertens’ “ovisae” has about the same position as these bodies, and he says he 
4 H 
MDCCCLI. 
