78 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
with the long axis antero-posterior, and the branchial and 
atrial apertures nearly terminal. The test is well developed. 
The musculature of the body-wall is in the form of a series 
of transversely-running bands, which do not form complete 
independent rings, as in the CycLomyaRIA. The branchial 
and peribranchial cavities form a continuous space in the 
interior of the body, opening externally by the branchial 
and atrial apertures, and traversed obliquely from the 
dorsal and anterior end to the ventral and posterior by a 
long, narrow, vascular band, which represents the dorsal 
lamina, the dorsal blood sinus, and the neighbouring part 
of the dorsal edge of the branchial sac of an ordinary 
Ascidian. The alimentary canal is placed ventrally. The 
embryonic development is direct, no tailed larva being 
formed. 
The Salpide, the chief family in this sub-order, includes 
the single genus Salpa, which, however, may be divided 
into two well-marked groups of species—(1) those, such 
as S. pinnata, in which the alimentary canal is stretched 
out along the ventral surface of the body, and (2) those, 
such as S. fusiformis, in which the alimentary canal forms 
a compact elobular mass, the ‘‘nucleus,”’ near the posterior 
end of the body. About fifteen species altogether are 
known; they are al] pelagic forms, and are found in many 
seas. Hach species occurs in two forms—the solitary 
asexual (proles solitaria) and the aggregated sexual (proles 
gregaria)—which are usually quite unlike one another. 
The solitary form gives rise, by internal gemmation, to a 
complex tubular stolon, which contains processes from 
all the more important organs of the parent body, and 
which becomes segmented into a series of buds. As the 
stolon elongates, the buds near the free end, which have 
become advanced in their development, are set free in 
groups, the members in which remain attached together 
