96 



TUNICATA SALPIANS 



the posterior end of the branchial sac. Hermaphrodite repro- 

 ductive organs lie ventrally near the intestine. 



This group is clearly distinguished from the second sub-order, 

 the Hemimyaria, by the condition of the muscle-bands and of the 

 branchial sac, and by the life-history. The muscle-bands are 

 complete rings (except in Ancliinia), while in the Hemimyaria 

 they are always more or less incomplete. The branchial sac 

 in the Cyclomyaria is a distinct cavity, and communicates with 

 the peribranchial cavity only by small slits or stigmata. The 

 Kfe-history is also very characteristic, as the sexual generation in 

 the Cyclomyaria is always polymorphic, while in the Hemimyaria 

 it consists of one form only. 



Structure of Doliolum. — The single family Doliolidab in- 

 cludes three genera, Boliolum, Quoy and Gaimard, Dolchinia, 

 Korotneff and Anchinia, Eschscholtz. Doliolum, of which about 



a dozen species 

 p.br are known, from 



has 



various seas, 

 a cask - shaped 

 body (Fig. 59), 

 usually from 1 

 to 2 cm. in 

 length. The ter- 

 minal branchial 

 and atrial aper- 

 tures are lobed, 

 and the lobes are 

 provided with 

 sense-organs. The 

 test is a thin but 

 tough transparent 

 layer, and con- 

 tains no " test " 

 cells. It is merely a cuticle covering the Surface of the squamous 

 ectoderm. The body-wall has eight or nine circular muscle-bands 

 surrounding the body. The most anterior and posterior of these 

 form the branchial and atrial sphincters. The wide branchial and 

 atrial apertures lead respectively into branchial and peribranchial 

 cavities separated by the posterior and postero-lateral walls of 

 the branchial sac which are pierced by a considerable number of 



Fig. 59. — Sexual generation of Doliolum tritonis, Herdman, 

 from left side, x 10. at, Atrial aperture ; atl, atrial 

 lobes ; at.m, wall of atrium ; br, branchial aperture ; br.l, 

 branchial lobes ; br.s, branchial sac ; d.t, dorsal tubercle ; 

 end, endostyle ; h, heart ; i, intestine ; m, mantle ; iii'-Tn?, 

 circular muscle-bands ; n, nerve ; n.g, nerve-ganglion ; ov, 

 ovary ; p.br, peribranchial cavity ; p.p, peripharyngeal 

 bands ; sg, stigmata ; s.gl, neural gland ; s.o, sense-organ ; 

 st, stomach ; t, test ; tes, testis ; z, prebranchial zone. 

 (After Herdman.) 



