74 ASCIDIANS CHAP. 
little or no food-yolk, and the tailed larvae (Figs. 26, 42, A) are 
of the typical form and structure described in Chapter IL. 
Fam. 3. Cynthiidae.—Solitary fixed Ascidians (Fig. 39), 
sometimes occurring in aggregations, but never forming colonies ; 
usually with leathery or fibrous, opaque test, which is sometimes 
encrusted with sand; branchial and atrial apertures usually both 
four-lobed. Branchial sac longitudinally folded (Fig. 36, A); 
stigmata straight; tentacles simple or compound (Fig. 37); 
eile 
Br f. |- 
~end---" 
Fic, 36.—Diagrammatic transverse sections of branchial sacs of Cynthiidae. A, Cynthia ; 
B, Styela ; C, Styelopsis ; D, Pelonaia. Br.f 1-7, First to seventh branchial fold ; 
d.l, dorsal lamina ; end, endostyle ; mh, meshes. 
neural gland dorsal to ganglion; gonads attached to body-wall. 
This family is divided into three sections :— 
Sub-Fam. 1. Styelinae.—Not more than four folds (Fig. 36, 
B) on each side of branchial sac; tentacles simple (Fig. 37, A). 
The more important genera are——Styela, Macleay, and Polycarpa, 
Heller (Fig. 39), with stigmata normal; and athyoncus, Herd- 
man, with stigmata absent or modified. There are a very large 
number of species of both Styela and Polycarpa, trom all parts of 
the world, including our own seas. A very abundant British 
littoral form has been placed in an allied genus under the name 
Styelopsis grossularia (Fig. 39, A). It is known in some places 
round our coasts as “ the red-currant squirter.” This species has 
only one well-marked fold in the branchial sac (Fig. 36, C). 
Another exceptional British Styelid is Pelonaia corrugata, Forb. 
and Goods. (Fig. 39, I), with no branchial folds (Fig. 36, D). 
