282 DB. W. A. HERDMAN ON BEITISH TUNICATA. 



Ascidia aspersa, Forbes fy Hartley, Brit. Moll. vol. i. p. 35 (1853). 

 Ascidia cristata, Grube, Ausflug nach Triest fyc, p. 65, tab. ii. fig. 8 



(1858). 

 Ascidia pustulosa, Alder, Ann, Sf Mag. Nat. Hist, ser, 3, vol. xi. p. 154 



(1863). 

 Ascidia aculeata, Alder, Ann. Sf Mag, Nat. Hist. ser. 3, vol. xi. p. 156 



(1863). 

 Ascidia cristata, Grube, Die Insel Lussin und ihre Meeresfauna, p. 53 



(1864). 

 Ascidia aspersa, Alder, Hebrid. Invert., Brit. Assoc. Rep. for 1866, p. 207 



(1867). 

 Phallusia pustulosa, Kupffer, Jahresberichte d. Komm, z. Untersuch. d. 



deutsch. MeereinKiel, Tan. p. 213 (1874). 

 Ascidia cristata, Heller, Untersuchungen it. d. Tan. Adriat. u. Mittelm. 



1 Abth. p. 16, Taf. vi. figs. 5-12 (1874). 

 Phallusia aspersa, Traustedt, Oversigt o. d. f. Dzmmark fyc, Asc. simp, 



p. 43(1880). 



This species varies somewhat in external appearance according 

 to its age, and there can be no donbt that Alder's A. pustulosa and 

 A. aculeata are merely the old and young stages. Grube suggests 

 that Delle Ohiaje's Ascidia mamillaris is a young specimen of this 

 species ; and the figure certainly closely resembles some small 

 specimens of A. aculeata from Lamlash Bay. Heller gives, under 

 the name of A. cristata, an excellent account of this species ; it 

 has also been well described as Phallusia pustulosa by Kupffer, 

 and as Ascidia aspersa by Traustedt ; in some of the internal cha- 

 racters, however, there is a certain want of agreement between 

 the various descriptions. In regard to the branchial sac, Alder 

 says that A. pustulosa has small papilla), and A. aculeata has 

 papillae and elliptical stigmata. Heller's description of the bran- 

 chial sac is good ; he refers to the longitudinal plication (like 

 that in Ascidia mentula), the long connecting ducts, and the very 

 small papillae. Kupffer, strange to say, mentions long papillae, 

 equalling in length the breadth of the meshes ; he may have con- 

 fused them with the long connecting ducts. In all the specimens 

 I have examined (from Lamlash Bay and Loch Long) the papillae 

 were very small, and, except when seen in profile, appeared as 

 mere thickenings of the internal longitudinal bars ; the meshes 

 were small and nearly square, containing each four to six rather 

 short stigmata (PI. XVI. fig. 1). 



The dorsal lamina, correctly described by Heller, is transversely 

 ribbed, and has the margin finely but irregularly denticulated 



