82. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
Sub-order IJ. Ascrp1a CoMmMPposiTa. 
Fixed Ascidians which reproduce by gemmation, so as 
to form colonies, in which the Ascidiozooids are buried in 
a common investing mass, and have no separate tests. 
This is probably a somewhat artificial assemblage, formed 
of two or three groups of Ascidians which produce colonies 
in which the Ascidiozooids are so intimately united that 
they possess a common test or investing mass. This is 
the only character which distinguishes them from the 
Clavelinide, but the property of reproducing by gemma- 
tion separates them from the rest of the Ascidize Simplices. 
The Ascidize Compositee may be divided into the following 
families :— 
Family I. Distomipa :—Ascidiozooids divided into two 
regions, thorax and abdomen; testes numerous; vas deferens 
not spirally coiled. The chief genera are—Distoma, Dis- 
taplia, Colella, the last forming a pedunculated colony, 
in which the Ascidiozooids develop incubatory pouches, 
opening from the peribranchial cavity, in which the 
embryos undergo their development. 
Family Il. Ca@iocormip#:—Colony not fixed, having 
a large axial cavity with a terminal aperture. Branchial 
apertures 5-lobed. This includes one species, Cawlocormus 
hualeyt, which is a transition form between the ordinary 
Compound Ascidians (e.g., Distomide) and the Ascidize 
Lucie (Pyrosoma). 
Family II. DipemMnipa:—Colony usually thin and 
incrusting. Test containing stellate calcareous spicules. 
Testis single, large; vas deferens spirally coiled. The 
chief genera are—Didemnum, in which the colony is thick 
and fleshy, and there are only three rows of stigmata on 
each side of the branchial sac; and Leptoclinum, in which 
the colony is thin and incrusting, and there are four rows 
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