86 ASCIDIANS 
CHAP. 
this genus there may be dimorphism in the buds, some of them 
\ i Ay D 
Fic. 48.—Transverse section of the abdomen of a 
Distomid. 6/.s, Blood-sinus ; ec, ectoderm ; 
ep.c, epicardium ; g/, intestinal glands ; h, heart ; 
i, intestine ; 7.m, longitudinal muscles ; mes, 
mesoderm ; 0.d@, oviduct ; p.c, pericardium ; sf, 
stomach ; v.d, vas deferens. (After Seeliger. ) 
placed deeply in the stalk 
having a large amount of 
reserve food-matter in their 
ectoderm, and remaining 
dormant until required to 
regenerate the “head” or 
upper part of the colony 
when it is lost. This genus 
was made known by the 
“ Challenger” expedition. 
The species are mostly trop- 
ical, or from southern seas. 
Fam. 2.Coelocormidae. 
—Colony not fixed, having 
a large axial cavity with 
a terminal aperture. Bran- 
chial apertures five-lobed. 
This includes one species, Coelocormus hualeyi, Herdman, which is 
in some respects a transition-form between the ordinary Com- 
pound Ascidians (eg. Distomatidae) and the Ascidiae Luciae 
(Pyrosoma, see p. 90). 
flees : 
Fic. 49. 
Section of Leptoclinum colony, showing the distribution of spicules and parts 
of the ascidiozooids. 6, Base of colony ; 67, branchial aperture ; 67.s, branchial sac ; 
sp, spicules ; s/, stomach ; fes, testis ; v.d, vas deferens. 
Fam. 3. Didemnidae.—Colony usually thin and incrusting. 
Test containing stellate calcareous spicules (Figs. 49 and 50, B). 
