STUDIES ON THE PROTOCHORDATA. 329 



topography of the mouth in the larvae of the Ascidians and 

 Amphioxus belongs to one and the same category, while 

 that of the mouth of Balanoglossus belongs to quite another 

 category. If it is desirable to speak of bilateral structures as 

 being dorsal or ventral, the pre-oral lobe of Amphioxus is, 

 palingenetically, ventral and not dorsal. 



In view of the numerous divergent opinions which have 

 recently been expressed with regard to the correspondence of 

 parts in the Protochordata and Chordata generally (KupflPer, 

 Hatschek, van Wijhe, DavidoflF), it is obvious how much 

 depends on a correct estimate of the asymmetrical mouth of 

 the larva of Amphioxus. 



Literature. 



Works cited in the first '' Study " and again referred to in 

 the foregoing pages have the numeral I prefixed to them. 



1. DoHKN, A. — Studien. Ill: "Die Entstehung uud Bedeutung der Hypo- 



physis bei Petromyzon planeri," 'Mitth. zool. Stat. Neapel,' iv, 

 1882, pp. 172—189. 



2. Ganin, M. — " Neue Thatsachen aus der Entw. der Ascidien," ' Zeit. f. 



wiss. Zool.,' XX, 1869-70, p. 512. 



3. Hatschek, B. — " Die Metamerie des Amphioxus und des Ammocoetes," 



' Verh. Anat. Gesellschaft in Wien,' 1892, pp. 136—161. 



4. Hekdman, W. a. — " On the Homology of the Neural Gland in the 



Tunicata with the Hypophysis Cerebri," *Proc. Boy. Soc. Edin.,' 

 xii, 1882-4, p. 145. 



5. Hjort, J. — "Zum Entwickelungscyclus der zusammengesetzten As- 



cidien," ' Zool. Anz.,' XV, 1892, 328—332. 



6. JuLiN, C. — " Rech. sur I'organisation des Ascidies simples : sur I'Hypho- 



physe," &c., 'Arch, de Biol.,' ii, 1881, pp. 59—126 and 211—232. 



7. KowAiEVSKY, A. — " Ueber die Entwickelung der Pyrosoma," ' Arch. f. 



mikr. Anat.,' xi, 1875. 



8. KuPFFEB, C. von. — "Zur Entwickelung der einfachen Ascidien," 'Arch. f. 



mikr. Anat.,' viii, 1872, pp. 358—395. 



