XTII 



THYLUM CHORD AT A 



29 



a series of papilhe. The colonies of Py 

 two or three inehes to 

 four feet in length, are 

 pelagic, and are bril- 

 liantly phosphorescent. 

 The enteric canal 

 in Appendicularia (Fig. 

 723) consists, in addi- 

 tion to the pharynx, of 

 a narrow a?sophagus, a 

 bilobed stomach, and a 

 straight intestine (int.) 

 which opens directly 

 by an anal aperture 

 {an.) situated on the 

 ventral side. The 

 alimentary canal of 

 the simple Ascidians 

 has already been de- 

 scribed, and there are 

 few differences of con- 

 sequence in the various 

 families, except that in 

 some cases there is a well -developed 



rosoma, which may be from 



A 



B 



Colony 



tcTvh 



ph. 



stoL 



atj'.ap 



G. 7.30,— Part of a section through a, Fyrosoma 

 colony. ati\ up. atrial aperture ; or. a/i. oral .aper- 

 ture ; proc. processes of test on outer surface of 

 colony ; ph. pharynx ; ."ftot. stolon on which are de- 

 veloped buds givint,^ rise to new zooids ; t^r/U. tentacles. 

 (After Herdnian.) 



of Fyrosoma. A, side view ; B, 

 icw. (After Herdiuan.) 



digestive gland or "liver"; 

 m the composite forms 

 the arrangement of the 

 parts -is the same in all 

 essential respects as in 

 the simple. In the Sal pa; 

 and in Doliolum and 

 Octacnemus the aliment- 

 ary canal forms a rela- 

 tively small dark mass — 

 the so-called nucleus — 

 towards the posterior end 

 of the body ; it consists 

 of oesophagus, stomach, 

 and intestine, the anal 

 aperture being situated 

 in the peribranchial or 

 atrial part of the internal 

 cavity. 



The heart in all has 

 the simple structure al- 

 ready described in the 

 simple Ascidian. In Ap- 

 pendicularia its wall 



