EEPOBT OK THE TUKICATA. 
313 
The nerre ganglion and neural gland form an ellipsoidal opaque mass, placed in the 
mantle over the prebranchial zone. The aperture of the dorsal tubercle is immediately 
on the ventral face of this mass, and opens between the base of the dorsal tentacle 
and the anterior end of the dorsal lamina. It is a longitudinally placed slit with raised 
edges (PI. XLII. fig. 13, d.t.). There is a very slight peritubercular area, but the 
tubercle really occupies nearly the entire breadth of the prebranchial zone. The region 
bounded by the peripharyngeal band (PI. XLII. fig. 13, p-p.) is nearly as wide from side 
to side as it is dorso-ventraUy. 
The oesophagus commences at the dorsal edge of the posterior end of the branchial 
sac, and runs backwards to open into the large globular smooth-walled stomach (PI. XLII. 
figs. 7, 8, 9, St.). The intestine, after leaving the posterior end of the stomach, curves 
round ventrally and then anteriorly in a wide open loop. It runs forwards to about the 
level of the oesophagus, and then turns dorsally at a sharp angle to become the rectum 
(PI. XLII. figs. 7, 8, 9) 'which crosses the oesophagus and so reaches the dorsal edge 
of the branchial sac. The rectum contains dark-coloured faecal pellets. 
The reproductive organs were not well developed in any of the Aseidiozooids 
examined ; but many of them showed buds in various stages of develoj^ment (see 
PI. XLII. figs. 7, 8). The method of budding is that first described by Macdonald, 
and since called pyloric budding by Giard. The thorax and the abdomen of the new 
Ascidiozooid arise as distinct buds^ from the body of the parent (PI. XLII. fig. 7, hr.s'. 
and st., i'.). 
Diplosoma, Macdonald. 
Didemnum, Milne-Edwards, Observations, &c., 1841. 
Dii>losoma, Macdonald, Trans. Linn. Soc. Lond., vol. xxxii. p. 373, 1858. 
Diplosoma, Psendodidemnvm, and Astdlium, Giard, Eecherclies, &c., 1871. 
• Pseudodidemmim, Astellium, Della Valle, Coiitribuzioni, &c., Kapoli, 1877. 
Dix>losoma, von Drascbe, Die Synascidien, 1883. In part. 
Diplosoma, Pseudodidemniim, a.wi\. BrevistelUum, 3 omAcdn,Con\'^^QS, XQTnilius,t. c. p. 1512, 1885. 
Colony usually thin and incrusting, rarely thick. 
Systems irregular. Common cloacal apertures rounded. 
Aseidiozooids dmded into thorax and abdomen. 
Test soft and gelatinous, usually transparent, sometimes pigmented, never with 
calcareous spicules. 
Branchial Sac large, with four rows of stigmata. 
Alimentary Caned moderately large. Stomach ellipsoidal and smooth-walled. 
Reproductive Organs close to the intestinal loop. Vas deferens straight. 
Gemmation pyloric. Larva gemmiparous. 
1 Possibly the two buds may have a common origin from the oesophageal region, such as Jourdain has described in 
the case of Diplosoma {Brevistellium) spongiforme {Comptes rendus, t. c.. No. 24, p. 1512, 1885). 
(ZOOL. CHALL. EXP. PART XXXVIII. — 1886.) 
Pp 40 
