82 



r 



ASCIDIANS 



2. The PARIETAL, or " peribranchial " type seen in the Holo- 

 somata, typically in the Botryllidae. 



The remarkable process of gemmation seen in the families 

 Didemnidae and Diplosomatidae, where the bud arises from at least 

 two rudiments, the one stolonial or epicardiac in origin, and the 



ass. 



FIG. 46. A, Ascidiozooid from a Bot- 

 ryllid colony ; B, ascidiozooid from 

 a Distomid colony ; C. ascidiozooid 

 from a Polyclinid colony. a, 

 Anus ; at, atrial aperture ; at.l, 

 atrial languet ; br, branchial aper- 

 ture ; cl, cloaca ; d.l, dorsal languet ; ec, ectoderm ; 

 end, endostyle, ep.c, epicardiac tube ; gl, intestinal rn 

 gland ; h, heart ; i, intestine ; n.g, nerve-ganglion ; 

 oes, oesophagus ; ov, ovary ; p.c, pericardium ; r, 

 rectum ; sg, stigmata of branchial sac ; sp, spermatic sacs ; 

 sph, sphincter ; st, stomach ; t, tentacle ; t.k, terminal 

 ampullae of vessels in test ; v, colonial vessels ; v.app, 

 " vascular appendage " (stolon). 



other formed by one or more oesophageal or intestinal outgrowths, 

 has been called " entero-epicardiac," but it may probably be re- 

 garded as a modification of the stolonial type. 



The marked differences in the appearance of the colonies of 

 Compound Ascidians is largely due to the methods of budding ; 

 and even in those of the stolonial type, where the budding is 

 practically the same in essential nature, the results may be very 

 different in superficial appearance, according as the buds are 



