TUNICATA. 389 



The following divisions are recognised : 

 Copelata* 



Acopa. 



(Appendicularia?). 



Oikopleura, Fritillaria. 



1) Ascidise. 



Simplices. 



Cynthia, Phallusia, Molgula. 

 Sociales. 



Clavellina. 

 Compositse. 



AmaiToecium, Botryllus. 



2) Lucise. 



Pyrosoma. 



3) Cyclomyaria. 



Doliolum, 



4) Thaliad*. 



Salpa. 



Bibliography. 



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

 Vogt, C, Kecherches sur les animaux inferieures de la Mdditerranee. II. Memoires de l'lnstitut 

 de Geneve. 1852.— Ganin, Zeitschr. f. w. Zool. Bd. XXV. 



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

 Journal of Microscop. Sc. 1856. — For,, H., Etudes sur les Appendiculaires. Mem. Soc. de 

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



Ascidiee : Sayigxy, Memoire sur les animaux sans vertebres. II. Paris, 1816. — Schalck, Deasci- 

 diarum structura. Halae, 1814. — Milne-Edwards, Observations sur les ascidies composers. 

 Paris, 1841. — Eschhicht, Videnskab. Selsk. Abhandl. IX. 1842. — Van Beneden, Memoire sur 

 l'embryogenie, l'anatomie, etlaphysiologie des Ascidies simples. Mem. de l'Academie Royale de 

 Belgique. T. XX. 1S40. — Metschnikoff, E., Ueberdie Larven und Knospen von Botryllus. Bull. 

 Acad, des Sc. de St. Fetersbourg. T. VI. — Krohn, A., Fortpflanzung von Botryllus. Archiv f. 

 Xaturgesch. 1869.— Kowaleysky, Entw. d. einf. Ascid. Mtm. Acad. imp. de St. Petersb. VTt. 

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

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

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

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



Lucias : Kowaleysky, A., Entw. von Pyrosoma. Arch. f. mikr. Anat. XI. — Panceri, P., Gli 

 organi luminosi dei Pirosomi. Atti del R. Accad. delle Sc. fis. e math. Napoli. V. 



Cyclomyaria : Krohn, Ueber die Gattung Doliolum. Arch. Nat. 1852.— Gegenbaur, Doliolum. 

 Zeitschr. f. wiss. Zool. 1S54. — Kefeestein u. Ehlers, Zoolog. Beitriige. Leipz. 1861. 



Tlialiadse : EscHRicnr, Undersogelser over Salpeme. Kjobenhavn, 1841. — Saes, Fauna litorahs 

 Norvegia?. I. — Krohn, A., Ann. sc. nat. III. vi. — Muller, H., Zeitschr. f. w. Zool. IV.— 

 Salexsky, Embryonal. Entw. d. Salpen. Z. f. wiss. Zool. XXVII.— The same, Ueber die Knos- 

 pung der Salpen. Morphol. Jahrb. III. 



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

 not 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 larva; of many Acopa have this directive organ. A much greater difference between 

 the two divisions is to be found iu the characters of their spiracles. In the Copelata 

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

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

 characteristic. 



