TUNICATA 



195 



are, therefore, not closely allied to the other Compound 

 Ascidians. The later Proto-Ascidiacea were probably 

 colonial forms, and gemmation was retained by the Clave- 

 linidx and by the typical Compound Ascidiana (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 Botryttidx and 

 the Polystydidx. 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 Proto-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 Tkaliacea ; and (3) the Ascidix Composite 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, Memoires sur les 

 Animauxsans Vertebres, pt ii. fasc. L, Paris, 1816 ; (j) Lamarck, 

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

 O. F. Miiller, Zool. Dcmica, vol. iv., 1806 ; (j) Milne-Edwards, 

 "Observ. s. les Ascidies Composees," &c., in Mem. Aead. Sei., 

 Paris, voL xviii., 1842 ; (6) Schmidt, Zur vergl. Physiol. d. wir- 

 bellos. Thiere, Brunswick, 1845 ; (7) Lowig and Kolliker, " De 

 la Compos., ic., d. EnveL d. Tun.," in Ann. Se. Nat., ser. 



iii. (Zool.), voL v. f 1846 ; (8) Huxley, Phil. Trans., 1851 ; (9) 

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

 Aead. Se., ser. vii, vol. x., 1866 ; (10) J. P. van Beneden, " Bech. 

 s. 1'Embryolog., Ac., d. Asc. Simp.," in Mem. Aead. Soy. Belg., 

 voL xx., 1847 ; (//) Krohn, in Weigmann and Miiller's Archiv, 

 1852 ; (12) Knpfler, Arch./. mOr. Anat., 1869, 1872 ; (13) Giard, 

 " fitude d. trav. Embryolog. d. Tun., &e.," in Arch. Zool. JSxper., 

 voL i, 1872 ; (14) Fol, " fitndea snr les Appendiculaires du Detroit 

 de Messine," in Mem. Soc. Phys. -Hist. Nat. Geneve, voL xxi. ; (tj) 

 Giard, " Reeherches s. L Asc. Comp.," in Arch. Zool. Exper., vol L. 

 1872; (16) Von Drasche, Die Synascidien der Bucht von Kovigno, 

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

 Challenger Expedition," pt i in Zool. Chall. Exp., vol. vi., 1882 ; 

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

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

 1870 ; (79) Heller, "Untersuch. n. d. Tunic, d. Adriat. Meeres," 

 in Denkschr. d. k. Akad. Wiss., 1875-77 ; (20) Laeaze-Duthiers, 

 " Asc. Simp. d. Cotes d. 1. Manch," in Arch. Zool. Exper., 1874, 

 1877; (21) Transtedt, in Vidensk. Mcdd. Naturh. For., Copenhagen, 

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

 Journ. Linn. Soc. Zool., voL xv., 1880 ; (23) Ussoff, in Proc. Imp. 

 Soc. Nat. Hist., Moscow, vol. xviiL, 1876 ; (24) John, "Rech. s. 

 1'Org. d. Asc. Simp.," in Arch. d. Biol., voL u., 1881 ; fey) Brooks, 

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

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

 Journ. d. I" Anat. et Phys., vol. xxi., 1885 ; (28) Uljanin, Fauna, 

 Ac., d. Golfes ton Neapel, voL x., 1884 ; (29) Moseley, " On Deep- 

 Sea Ascid.," in Trans. Linn. Soc., ser. ii., voL L, 1876 ; (30) E. van 

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

 vi., 1886 ; t?/) Lankester, Degeneration (Nature series), London, 

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

 Zool. Slat. Neapel. 



(W. A. HE.) 



PEIKTED BY XEILL AXD COMPANY, EDIXBUKGH. 



