80 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
members are not buried in a common investing mass, 
but each has a distinct test of its own. No strict line of 
demarcation can be drawn between the Simple and Com- 
pound Ascidians, and one of the families of the former 
group, the Clavelinide (the Social Ascidians), forms a 
transition from the typical Simple forms, which never 
reproduce by gemmation to the Compound forms, which 
always do. 
The Ascidize Simplices may be divided into the follow- 
ing families :— 
Family I. CLAVELINIDH:—Simple Ascidians which 
reproduce by gemmation to form small colonies, in which 
each Ascidiozooid has a distinct test, but all are connected 
by a common blood-system. Buds formed on stolons, 
which are vascular out-growths from the posterior end of 
the body containing prolongations from the ectoderm, 
mesoderm, and endoderm of the Ascidiozooid. Branchial 
sac not folded; internal longitudinal bars usually absent ; 
stigmata straight; tentacles simple. 
This family contains three chief genera—Hcteinascidia, 
with internal longitudinal bars in branchial sac; Clavelina, 
with intestine extending behind branchial sac; and Pero- 
phora, with intestine alongside branchial sac. Clavelina 
lepadiformis and Perophora listert are common British 
species found at a few fathoms depth off various parts 
of our coast. Both occur round the south end of the Isle 
of Man. 
Family II. Ascrp1rpa :—Solitary fixed Ascidians with 
celatinous test; branchial aperture usually 8-lobed, atrial 
aperture usually 6-lobed. Branchial sac not folded; in- 
ternal longitudinal bars usually present; stigmata straight 
or curved; tentacles simple. 
This family contains, along with several other genera, 
