TUNICATA. 389 



The following divisions are recognised : 

 Copelata.* 



Acopa, 



(Appendicularise). 

 Oikopleura, FritiUaria. 



1) AscidiEB. 



Simplicea. 



Cyuthia, Phallusia, Molgula. 

 Sociales. 



Clavellina. 

 Compositse. 



Amarroecium, Botryllus. 



2) LuciEe. 



Pyrosoma. 



3) Cyclomyaria. 



Doliolum 



4) ThaliadjB. 



Salpa. 



Bibliography. 



HcsLKT, Observations on the Structure of Salpa and Pyrosoma. Transact. Royal Soc. Lond. 1851.— 



VoGT, C, Recherches snr les animaux inferienres de la M^diterran^e. II. M^moires de 1 Institut 



de Geneve. 1852.— Ganik, Zeitschr. f. w. Zool. Bd. XXT. 

 Copelata : Gegenbaub, Zeitschr. f. w. Zool. VI.— Huxley, Further observations, etc. Quarterly 



Journal of Microscop. So. 1S56.— Fol, H., Etudes sur les Appendiculaires. M^m. Soc. de 



physique et d'hist. nat. de Genfeve. XXI. 

 Ascidise : Savignt, Memoire sur les animaux sans vertebres. 11. Paris, 1816.— Schalck, Deasci- 



diarnm strnctura. Halae, 181-i.— Milne-Edwabds, Observations sur les ascidies compos^es. 



Paris, 1841.— EscHEiCHT, Videnskab. Selsk. Abhandl. IX. 18i2.— Vau Beneden, M(5moire sur 



I'embryog^nie, I'anatomie, etlaphysiologie des Ascidies simples. Mi5m. de I'Academie Royale de 



Belgique. T. XX. 1846.— Metschnikofp, B., Ueberdie Larven und Knospen von BotryUus. Bull. 



Acad, des Sc. de St. P(;tersbourg. T. VI.— Keohn, A., Fortpflanzung von Botr.yllus. Archiv f. 



Naturgesch. 1869.— Kowalevskt, Entw. d. einf. Ascid. Mem. Acad. imp. de St. Petersb. VII. 



Ser. X.— The same, Ueber die Knoppung der Ascidien. Arch. f. mikr. Anat. X.— Kupffee, C, 



Z. Entw. d. einf. Ascidien. Arch. f. mikr. Anat. VIII.— Hektwig, R., Zur Kenntnis des Banes 



der Ascidien. Jenaische Zeitschr. VII.— Giaed, A., Rech. sur les Asc. comp. Arch, de Zool. I. 



— Lacaze-Dpthiees, H. de, Les Asc. simples des cotes de France. Arch. d. Zool. III. 

 LuciSB : Kowalevskt, A., Entw. von Pyrosoma. Ai-ch. f. mikr. Anat. XE — Pancbei, P., Gli 



organi luminosi dei Pirosomi. Atti del R. Acoad. delle Sc. fis. e math. NapoU. V. 

 Cyclomyaria : Khohn, Ueber die Gattung Doliolum. Arch. Nat. 1852.— Gegenbaue, Doliolum. 



Zeitschr. f. wiss. Zool. 1S51.— Kefebstein u. Ehlees, Zoolog. Beitrilge. Leipz. 1861. 



Thaliadse : Eschbicht, Undersogelser over Salpeme. Kjobenhavn, 1841.— Sabs, Fauna Htoralis 

 Norvegiee. I.— Keohn, A., Ann. sc. nat. III. vi.— Mullek, H., Zeitschr. f. w. Zool. IV.— 

 Salenskt, Embryonal. Enhv. d. Salpen. Z. f . wiss. Zool. XXVn.— The same, Ueber die Knos- 

 pung der Salpen. Morphol. Jahrb. III. 



* These two classes were formerly separated according to whether they had or had 

 Dot a propelling tail, as the names of the classes showed ; I have retained the nomen- 

 clature without giving an importance to this character, which does not belong to it ; 

 the larvae of many Acopa have this directive organ. A much greater difference between 

 the two divisions is to he found in the characters of their spiracles. In the Copelata 

 these open to the exterior. In the Acopa they open into a cavity, which is formed 

 from a part of the rudimentary spiracle of the Copelata. This is the most essential 

 characteristic. 



