PHYLUM TTJNICATA (UROCHORDA). 



aie 



other, saddle-shaped, becomes the atrium of the bud. The organs 

 formed in the usual way, the pericardium and intestine as outgrowths oi 



the pharynx and the 

 from 

 The 



Eel 



-1" 



FIG. 24. Diagram <>i a ilorsal view of a young oozoid or of a 

 bud of Botryllus violaeeus (after Pizon, from Perrier). B fu- 

 ture mouth ; bl rudiment of new blasto-zooid of one side ; 

 c.vib vibratile tube ; ect ectoderm ; gh gonad ; i intestine ; 

 perb peribranchial sac (atrial cavity) ; pv epicardical di- 

 verticulum ; vb pharynx ; Vcl cloacal part of future atrial 

 cavity. 



nervous system 

 the endoderm. 

 original connection re- 

 mains throughout life 

 as the vascular ecto- 

 dermal tube referred 

 to above. 



Botryllus Gartner 

 and Pallas (Fig. 23), 

 colony thin, encrust- 

 ing, systems circular, 

 gonads paired, placed 

 laterally, littoral, Eur., 

 Med., N. Amer. Poly- 

 cyclus Lamarck, as 

 last, but colony thick 

 and fleshy, Eur. and 

 Med. Botrylloides H. 

 Milne - Edw., colony 

 thin encrusting, sys- 

 tems elongated or 

 branched irregularly, 

 gonads paired, lateral. 

 Sarcobotrylloides v. 

 Symplegma Herdman, 



Drasche, like *last, but colony thick and fleshy. 



colony stalked, gonads unpaired, in intestinal loop, Bermuda. 



Fain. 2. Distomidae. Colony rounded or massive, rarely encrusting, 

 either sessile or with long peduncle ; systems irregular, inconspicuous or 

 absent, both mouth and atrium usually opening on 

 the surface of the colony. Zooids divided into thorax 

 and abdomen, and sometimes provided with long vas- 

 cular ectodermal appendages ; test gelatinous or cartila- 

 ginous, sometimes with non-stellate calcareous spicules ; 

 pharynx without internal longitudinal bars ; dorsal 

 lamina as langxiets ; gonads and heart in or alongside 

 intestinal loop, spermatic vesicles numerous, vas de- 

 ferens straight. 



In the Distomidae the budding is epicardial. The 

 epieardiuni arises as a pair of diverticula of the 

 pharynx, one <m each side of the oesophagus. The right 

 of these detaches a pericardium, then separates from 

 the pharynx and becomes connected to the left tube to 

 t'.inn t In- ili-tinite epicardial tube. This pushes out the 

 i-.-t.idrrm and forms a ventral stolon, which buds off 

 small free bodies into the test ; these may multiply 

 l>v tissioii and eventually develop into new zooids.* 

 In < 'olclla some of the buds, those placed in the deeper 

 p irts of the stalk, have a store of reserve food material in their ectoderm. 



FIG. 25. Distaplia 

 (after Herdman 

 ironi Delage and 

 Herouard). 



, op. c'lt. J uliii, 1 nt (Jong. Zoology, Leyden, JStKi. 



