108 



TUNICATA. 



Order 1. DESMOMYAEIA 



Thaliacea of cylindrical, usually dorso-ventrally flattened form, with 



band-shaped muscular hoops and thick mantle (fig. 566). The 



FIG ' 68. The forms of Doliolum der.ticuiatum (a, b, d, e, after C. Grobben ; c, after Gegenbaur). 

 a, Sexual animal. 0, Mouth ; A, cloacal aperture; Kl, cloacal space; N, nerve centre; 

 Hs, cutaneous sense organ ; Wb, arch of cilia ; Wg, ciliated pit ; End, endostyle ; Br, gills ; 

 C, heart ; D, intestine ; T, testis ; Ov, ovary ; M, muscular hoops, b, First asexual 

 generation. Stv, Ventral stolon ; Std, dorsal stolon ; Ot, auditory organ, c, A later stage 

 of 6, with developed dorsal stolon and aborted intestine and gills, less highly magnified. 

 Ms, Median buds ; Ls, lateral buds, d, Nutritive animal produced from the lateral buds 

 with large mouth and without cloaca ; Oe, oesophagus, e, Doliolum larva with larval tail ; 

 Ch, chorda (urochord). 



anterior opening is furnished with a valve-like lip which can be shut 

 down. The gill reaches from the ganglion to the oral region, and in 

 consequence of the development of two large lateral branchial slits 



