444 PEOF. W. A. HERDMAN ON BEITISH TUNICATA. 



Pamily Ctnthiid^.* 



Subfamily SiTELiisriE. 



POLTCAEPA GLOMEEATA (Alder). (PL XXXV. figS. 8-13.) 



This species is probably very abundant on yarious parts of 

 our coast, but has often, I think, been regarded as Styela rustica, 

 or Styelopsis grossularia ; it is, however, perfectly distinct from 

 both. This is a gregarious form like Polycarpa aggregata, and 

 although the tests of neighbouring individuals may fuse so 

 as to form a continuous basal expansion or common test (see 

 PI. XXXV. fig. 8), still there is no further organic connection 

 between the individuals ; there are no common vessels and no 

 buds are producedj consequently no true colony is formed, 

 and the masses, which may be yards in extent, are merely aggrega- 

 tions of individuals adhering together. 



There is a huge cavern near Spanish Head, at the south end 

 of the Isle of Man, which can be entered in a boat at low tide, 

 and its walls and part of the roof are covered by a continuous 

 layer of this Ascidiau. The individuals are of all sizes from a 

 small pin's head up to nearly an inch across, they are of a rich 

 crimson-red colour, and when touched they emit the usual jets 

 of water forcibly and in all directions. Hence they are known 

 locally as the " red-currant squirters of the sugar-loaf cave." 



Good descriptions of this species have been given by Heller f, 

 Traustedt J, and by E<oule §, so there is no need to go over the 

 characters in detail. The chief points which distinguish it from 

 other British Styelinse with which it might be confused are : — 

 the agglomerated condition, the brilliant colour, the presence of 

 more than one (usually 3) fold on each side of the branchial sac, 

 and the condition of the reproductive organs— broken up into 

 numerous polycarps each of which is of one sex only. 



I find that this is one of those interesting species in which 

 tentacles are present at the base of the atrial as well as of 

 the branchial siphon. They are very numerous but minute 

 (PI. XXXV. fig. 10). In regard to their possible function, I 



* For the characters of the family and subfamily see Herdman's " Eevised 

 Classification of the Tmiicata," Journ. Linn. Soc, Zool. vol. xxiii. p. 509. 



t Untersuch. u. d. Tunicaten d. Adriat. u. Mittelmeeres, iii. Abth. p. 263 

 (1877). 



\ Mitth. a. d. Zoolog. Stat, zu Neapel, t. iv. 



§' Eecherches sur les Ascidies Simples des Cotes de Provence," Biblioth. de 

 I'Ecole des Hautes Etudes, t. xxxi. art. no. 8, p. 150 (1685). 



