Broad-leafed Hormurack. 71 



The internal anatomy of the species here described resembles in 

 many points that of the Ascidian, AscitUa P/msea, figured by 

 Cuvier, Memoires du Museum, tom. ii., 1815, i^l. l, fig. g, 

 and described by him, I. c. pp. 29, 30 ; or Memoires pom- servir 

 k FHistoire et a FAnatomie des Mollusques, Memoire sur les 

 Ascidies, pp. 20, 21. The mouth is similarly situated at the 

 bottom of the branchial sac in Ascidia Scahra, which differs 

 from this species, Ascidia Affmis, in being smaller and rougher 

 externally. 



23. Broad-leafed Hornwrack {Flustra FoUacea). 



A Seaweed-like Polyzoon, very common and universal in Euro- 

 pean seas. The Polyzoary is flexible, of silk-like texture and ap- 

 pearance, ordinarily forming erect fronds but occasionally loosely 

 adnate to marine objects. The cells, which by their mutual appo- 

 sition in these social animals form the Polyzoary or Coenoeciiun, 

 are arranged multiserially in parallel longitudinal rows on both 

 sides of the frond they make up. The individual cells are ovoidal 

 in shape, and have from four to eight spines set round their larger 

 end, in which their mouth, which is crescentic and protected by 

 a lip, is placed subterminally. The avicularium and mandible are 

 semicircular and immersed. There are no vibracula. The polypide 

 itself is, when contained in its cell, bent several times upon itself. 

 Its tentacles are very long. It resembles the great majority of 

 fresh-water Polyzoa in the absence of a gizzard. The ovicell, a 

 sort of marsupial pouch, analogous, in respect of function, if not 

 homologous, with the cloaca of the Ascidians, and continuous with 

 the perivisceral space through a passage at the upper and back part 

 of each cell, is inconspicuous in this species, being deeply immersed. 

 The ova themselves are of a striking colour, and, as in other 

 Polyzoa, are set free by the death and disruption of the parent 

 polypide. 



For excellent figures of the external and internal anatomy of this 

 animal, see Van Beneden, Recherches sur TAnatomie, la Phy- 

 siologie, et le Developpement des Bryozoaires qui habitent la 

 cote d'Ostende, Mem. Acad. Royalc de Bruxelles, tom. xviii., 



