TUNIOATA 



195 



are, therefore, not closely allied to the other Compound 

 Ascidians. The later Proto-Aseidiacea were probably 

 colonial forms, and gemmation was retained by the Clave- 

 linidx and by the typical Compound Ascidians (Distomidx, 

 &c.) derived from them. The power of forming colonies 

 by budding was lost, however, by the primitive Simple 

 Ascidians, and must, therefore, have been regained inde- 

 pendently by the ancestral forms of the Botryllidx and 

 the Polystyelidx. If this is a correct interpretation of the 

 course of evolution of the Tunicata, we arrive at the 

 following important conclusions. (1) The Tunicata, as a 

 whole, form a degenerate branch of the Froto-Chordata ; 

 (2) the Ascidix Salpiformes (Pyrosoma) are much more 

 closely related to the typical Compound Ascidians than 

 to the other pelagic Tunicata, viz., the Larvacea and 

 the Thaliacea ; and (3) the Ascidiee Compositas form a 

 polyphyletic group, the sections of which have arisen 

 at several distinct points from the ancestral Simple 

 Ascidians. 



Bibliography. — (/) Cuvier, "Mem. s. les Ascidies," &c., in Mem. 

 d. Mus., vol. ii. p. 10, Paris, 1815 ; {2) Savigny, M6moires sur les 

 Animauxsans Vertibres, pt. ii. fasc. i., Paris, 1816; (^) Lamarck, 

 Hist Nat. d. Anim. sans Vertibres, 1st ed., Paris, 1815-23 ; (4) 

 O. F. Miiller, Zool. Danica, vol. iv., 1806 ; (5) Milne -Edwards, 

 " Observ. s. les Ascidies Composees," &c., in Mim. Acad. Sci., 

 Paris, vol. xviii., 1842 ; (6) Schmidt, Zur iiergl. Physiol, d. wir- 

 bellos. Thiefe, Brunswick, 1845 ; (7) Liiwig and Kblliker, " De 

 la Compos., &c., d. Envel. d. Tun.," iu Ann. So. Nat., ser. 



iii. (Zool.), vol, v., 1846 ; (,?) Huxley, Phil. Trails., 1851 ; (p) 

 Kowalevsky, " Entwickel. d. einf. Ascid.," in Mem. St. Petersb. 

 Acad. Sc., ser. vii., vol. x., 1866 ; (/o) J. P. van Beneden, " Kech. 

 s. rEmbryolog., &c., d. Asc. Simp.," in Jf^m. Acad. Roy. Belg., 

 vol. XX., 1847 ; {11) Krohn, in Weigmann and Miiller's Archiv, 

 1852 ; {12) Kupffer, Arch. f. mikr. Anat., 1869, 1872 ; (ij) Giard, 

 " fitude d. trav. Embryolog. d. Tun., &c.," in Arch. Zool. Expir., 

 vol. i., 1872 ; {i4) Fol, " iitudes sur les Appendiculaires du Detroit 

 de Messine," in Mira-. Soc. Phys. Hist. Nat.' Genive, vol. xxi. ; (/j) 

 Giard, " Eecherches s. 1. Asc. Comp.," in^reA. Zool, Exper., voli., 

 1872 ; {16) Von Drasche, Die Synasddien der Bueht von Momgno, 

 Vienna, 1883 ; (77) Herdman, "Report upon the Tunicata of the 

 Challenger Expedition," pt. i. va. Zool. Ghall. Exp.,\d\. vi., 1882 ; 

 pt. ii. in Zool. Chall. Exp., vol. xiv., 1886 ; pt. iii. not yet pub- 

 lished ; (/<?) Alder and Hancock, in Ann. Mag. Nat. Hist., 1863, 

 187.0; (79) Heller, " Untersuch. u. d. Tunic, d. Adriat. Meeres," 

 in Denkschr. d. k. Akad. Wiss'., 1875-77 ; {20) Lacaze-Duthiers, 

 "Asc. Simp. d. C6tes d. 1. Manch," in ^reft. Zool. Exper., 1874, 

 1877; (27) Traustedt, in Vidensk. Medd. Naturh. For., Copenhagen, 

 1881-84; {22) Herdman, "Notes on British Tunicata, &c,," in 

 Journ. Linn. Soc. Zool., vol. xv., 1880 ; (sj) Ussoff, in Proc. Imp. 

 Soc. Nat. Hist., Moscow, vol. xviii., 1876 ; (24) Julin, " Rech. s. 

 rOrg. d. Asc. Simp.,", in Arch. d. Biol., vol. ii., 1881 ; (25) Brooks, 

 " Development of Salpa," in Bull. Mus. Comp. Zool., Harvard, vol. 

 iii. p. 291 ; (26) Salensky, Ztschr. f. wiss. Zool., 1877 ; (27) Barrois, 

 Jown. d. I Anat. et Phys., vol. xxi., 1885 ; (28) Uljanin, Faurm, 

 &c., d. Oolfes von Neapel, vol. x., 1884 ; (29) Moseley, " On Deep- 

 Sea Ascid.," in Trans. Linn. Soc, ser. ii., vol. i., 1876 ; (jo) E. van 

 Beneden and Julin, "Morph. d. Tuniciers," in Arch. d. Biol., vol. 

 vi., 1886 ; {31) Lankester, Degeneration (Nature series), London, 

 1880; (32) Dohrn, "Stud. z. Urgesch. d. Wirbelth.," in Mitth. 

 Zool. Stat. Neapel. 



(W. A. HE.) 



PRINTED BY NEILL AKD COMPANY, EDIKBUKGH. 



