BOTRYLLUS. 19 



2. D. vARioLosuM, Gaertner. 



Alcyonium ascidioides, Pallas, Sp. Zool. f. 10, p. 40, f. 4, f. 7, a, A. — A. di- 

 stomum, Brugiere, Enc. Meth. — Distoma variolosum, Savigny, Mem. 2nd 

 part, p. 178. — Polyzona variolosa, Fleming, Br. An. p. 469. 



Mass coriaceous, not thick, flat beneath, warty above ; pale 

 reddish, or yellowish-white. Individuals orange- red. Systems 

 not distinctly circumscribed. 



" Common on Fucus palmatus, and on that plant only, enve- 

 loping sometimes the entire stem," according to Gaertner. " A Di- 

 stoma, apparently, from description, of this species, has occurred to 

 me investing Fucus serratus in Belfast Bay : the colour was al- 

 ways whitish-yellow," W. Thompson, Ann. N. H. vol. v. p. 95. 



BOTRYLLUS, Gaertner. 



This genus, one of the first established among the Com- 

 pound Ascidians, is the type of the tribe of " Botryllians" in 

 the arrangement of Mihie-Edwards. The individual animals 

 present no distinction between abdomen and thorax. Their 

 viscera are accumulated in the thoracic cavity, and form 

 with it an ovoid mass. Their branchial orifices are simple : 

 they are ranged round a common cloaca. In the genus 

 Botryllus they are grouped in simple stars, and lie hori- 

 zontally, with the vent far from the branchial orifice. 



1. B. ScHLossERi, Pallas, (Sp.)* 



chlosser, Phil. Trans, vol. xlix. pt. 2, 1757, p. 447, t. 14, fig. a — c ; Borlase, 

 Nat. Hist. Cornwall, p. 254, t. 25, f. 1, 2, 3, 4. — Alcyonium Schlosseri, Pallas, 

 Elench. Zooph. No. 208. — Botryllus stellatus, Gaertner in Pallas, Spic. Zool. 

 fesc. 10, p. 37, t. 4, f. 1 — 5. — B. stellatus, Brugiere, Enc. Meth. 1 ; La- 

 marck. — B. Schlosseri, Savigny, Mem. pt. 2, p. 200, pi. 20, f. 5 ; Fleming, 

 Brit. An. p. 470. — Alcyonium Schlosseri, Linnaeus, Syst. Nat. 12th ed. — A. 

 Schlosseri, Ellis and Solander, Nat. Hist. Zooph. p. 177. 



Plate A, fig. 7, and plate B, fig. 7. 

 Mass a thick, gelatinous, semi-transparent, glaucous crust, with 

 yellow marginal tubes. Systems numerous, composed of from ten 



* In the forty-ninth volume of the" Philosophical Transactions" (for 1756) occurs 

 the first notice of the Compoimd Ascidians, being the description of this Botryllus, 

 with a very characteristic figure. The paper is entitled, "An account of a curious 



