4 MM. Kowalevsky and Barrois on Anchinia. 
tion ; on the other hand the median portion of the cloaca attains 
a considerable development, and has a volume nearly equal 
to that of the pharyngeal cavity. 
Anchinia presents this interesting peculiarity :—As regards 
the arrangement of the great cavities and of the branchia it 
represents the exact intermediary between the above two great 
types, Pyrosoma and Doliolum. Init the median portion ot the 
cloacal cavity is already large, but its dimensions are still 
very restricted as compared with those of the pharyngeal sac ; 
its lateral parts are likewise better marked off from the median 
portion than in Doliolum, but incomparably less developed 
than in Pyrosoma, and only cover a small portion of the 
pharyngeal sac. Lastly, the branchia consists, as in Doliolum, 
of a single series of long clefts parallel to the endostyle; but 
it is wider than in Doliolum (fig. 8), and in this respect some- 
what approaches that of Pyrosoma. 
Anchiniais certainly the most complete transition type that 
we know between the Salpa form and the Ascidia form, re- 
garded as representing the two extreme types from the stand- 
point of the arrangement of the two great cavities. It is the 
most instructive form to study for any one who wishes to form 
a notion of these important relations. 
I pass now to a more detailed description :— 
1. General form.—The body is very short and thickset, 
not at all elongated in the form of a little barrel, but extended 
especially in the direction of its height; its general aspect 
does not at all resemble that presented by the Doliola, but 
nearly approaches that of the lateral buds destitute of cloaca 
which are observed upon their tails. 
2. Cloaca.—F ig. 8 shows the boundaries of the median and 
lateral portions of the cloaca. ‘The line /m indicates the limit 
of the median portion, and the line /¢ that of the left lateral 
expansion. <A little above the buccal aperture (d) there is a 
point () where the median portion comes almost into contact 
with the pharyngeal sac, which causes the lateral expansion 
to appear divided into two distinct parts—an inferior very 
large one (c/) covering the digestive tube, and a superior very 
small one (/s) only surrounding a vacant space belonging to 
the general cavity, a space which, in the living animal seen 
in profile, appears as a triangular part of dark colour, already 
seen and figured by Vogt, who, however, did not attempt to 
give any explanation of it. 
3. General cavity The two great cavities (pharyngeal 
and cloacal) so completely occupy the interior of the body that 
there remains only a mere fissure to represent the general 
cavity. We ebserve, however, two great -dilatations—one 
