MM. Kowalevsky and Barrois on Anchinia. 3 
of the stolonin much detail ; we have not seen muscular fibres 
in it; it appeared to us to be a simple hollow tube, formed of 
a single series of epithelial cells, and enveloped in a very thick 
tunic, containing here and there stellate cells. The most 
remarkable thing to be noted in the stolon is a series of large 
cells (Pl. II. fig. 1, c) superimposed upon the epithelium, and 
placed upon the median line between the zooids. 
The latter are arranged upon a somewhat irregular line and 
[each] implanted upon a slight projection formed by the epi- 
thelium of the stolon; this projection is separated from the 
peduncle by a double septum composed of epithelial cells ; 
these septa separate at the period when the bud becomes de- 
tached from the stolon. 
I. Description of Anchinia. 
Anchinia (Pl. III. fig. 8), like Pyrosoma and Doliolum, is 
a type of Tunicate in which the two apertures, incurrent and 
excurrent, are directly opposite to each other. The two 
cavities to which they give access, namely the pharyngeal sac 
(Ph) and the median portion of the cloaca (cm), are not, as in 
the Ascidia, attached to one another, but they face each other, 
and are situated at the two extremities (fie. 8). Between the 
two there is a space in which the digestive tube is lodged. In 
consequence of the separation of these two large cavities, the 
digestive tube, which in the Ascidia is situated below these 
cavities, is included between them in Anchinia; it is more- 
over surrounded to the right and left by the lateral expan- 
sions of the cloaca (cl), which spread over the pharyngeal sac 
to form the branchia. It is therefore included in a sort of 
case, which only communicates above and below with the 
rest of the general cavity. Hig. 11, which represents a trans- 
verse section passing through the two apertures, will serve 
better than any explanation to render this arrangement intel- 
ligible. 
Pyrosoma and Doliolum also present the same arrangement 
but with differences which it is important to note. In Pyro- 
soma the median portion of the cloaca is exceedingly small, 
in fact quite rudimentary, and out of all proportion to the 
pharyngeal sac, which occupies an enormous space. Its 
lateral portions, on the contrary, are much developed, and 
completely cover the whole of the pharyngeal sac, the entire 
wall of which is converted into branchia. 
In Doliolum it is quite otherwise. The lateral portions of 
the cloaca are rudimentary ; they do not cover the pharyngeal 
sac, of which the branchia occupies only the posterior por- 
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