38 ASCIDIANS CHAP. 
branch from the lower end of the phylum CHorpata, which 
includes the Tunicata (or Urochordata), Balanoglossus and its 
allies (Hemichordata), Amphioxus (Cephalochordata), and the 
Vertebrata (or Craniata). Kowalevsky’s great discovery has 
since been confirmed and extended to all other groups of the 
Tunicata by Kupffer,’ Giard, and others. 
In 1872 Fol” added largely to the knowledge of the 
Appendiculariidae, and Giard*® to that of the Compound 
Ascidians. The latter author described a number of new forms 
and remodelled the classification of the group. The most 
important additions which have been made to the Compound 
Ascidians since Giard’s work have been the species described by 
von Drasche,* from the Adriatic, and those discovered by the 
“Challenger ” expedition.? The structure and the systematic 
arrangement of the Simple Ascidians have been discussed of 
recent years mainly by Alder® and Hancock, Heller,’ Lacaze- 
Duthiers,> Traustedt? Roule, Hartmeyer, Sluiter’? and Herd- 
man.'' In 1874 Ussoff investigated the minute structure of 
the nervous system and of the underlying gland, which was first 
discovered by Hancock, and showed that the gland has a duct 
which communicates with the front of the branchial sac or 
pharynx by an aperture in the dorsal (or “ olfactory ”) tubercle. 
In an important paper published in 1880, Julin ” drew atten- 
tion to the similarity in structure and relations between this 
gland and the “ hypophysis cerebri” of the Vertebrate brain, and 
insisted upon their homology. Metcalf has recently added 
further to our knowledge on this and related matters. 
The Thaliacea or pelagic Tunicata have of late years been 
the subject of several very important memoirs. The researches 
Arch. mikr. Anat. vi. 1872. 
Mém. Soc. Phys. Hist. Nat. Geneve, xxi. 1872. 
Arch. Zool. Expér. i. 1872. 
Synascidien der Bucht von Rovigno, Wien, 1883. 
Challenger Reports, Tunicata, Part i. vol. vi. 1882; Part ii. vol. xiv. 1886; 
Part iii. vol. xxvii. 1888. 
8 Ann. Mag. Nat. Hist. (3) xi. 1863, p. 153; Journ. Linn. Soc. 1868, etc. 
7 Denkschr. Akad. Wiss. Wien, 1875 and 1877. 
8 Arch. Zool. Expér. iii. 1874, and vi. 1877 ; Mém. Instit. Paris, xlv. 1892. 
9 Vid. Medd. Nat. For. Copenhagen, 1880, 1882, 1884, etc. 
10 Nat. Tijdschr. Ned.-Indie, 1885, ete. 
1 Journ. Linn. Soc. Zool. xv. xxiii. and xxiv. ; Cat. of Tunicata in Australian 
Museum, 1899 ; also Challenger Reports (see note 5). 
12 Arch. de Biol. ii. 
a p © to 
