232 EMBRYOLOGY 



expounder of this view, compares to the central nervous system of the 

 Vertebrata the dorsal nerve cord found by him. The cerebral ganglia of 

 the Nemerteans are held to correspond to the series of ganglia of the 

 cranial nerves of the Vertebrata, and the lateral nerves to the nervi 

 laterales which occur so constantly in the latter group. In the chorda 

 HuBRECHT sees the metamorphosed sheath of the proboscis, while the 

 remnant of the proboscis itself would be recognized in the hypophysis. 

 For this view Hubkecht finds support in the fact that in certain Nemer- 

 teans the proboscis opens out in the vicinity of the oesophagus, and that 

 in Tetrastemma it is said even to arise from the wall of the oesophagus 

 (Hoffmann, No. 7). For the present these explanations have only the 

 value of a mere hypothesis. 



Literature. 



1. Barrois, J. M^moire sur I'embryogenie des Nemertes, Ann. Set. 

 Nat. (ser, vi.) Zoologie Tom. vi. 1877. 



2. BuTscHLi, 0. Einige Bemerkungen zur Metamorphose des 

 Pilidium. Arch. Naturgesch. Jahrg. xxxix., Bd. i. 1873. 



3. Desor, E. Embryologie von Nemertes. Arch. Anat. n. PTiys. 

 Jahrg. 1848. 



4. DiECK, G. Beitrage zur Entwicklungsgeschichte der Nemertinen. 

 Jena. Zeitschr. Bd. viii. 1874. 



5. Fewkes, J. W. On the Development of Certain Worm Larvae. 

 Ball. Mus. Comp. Zobl. Harvard College, Cambridge, Mass. Vol. xi. 

 1883—1885. 



6. GegenbauRj'C. Bemerkungen iiber Pilidium, Actinotrocha, und 

 Appendicularia. Zeitschr. wiss. Zool. Bd. v. 1854. 



7. Hoffmann, C. K. Beitrage zur Kenntniss der Nemertinen : I. Zur 

 Entwicklungsgeschichte von Tetrastemma varicolor Oerst. Niederl. 

 Arch. Zool. Bd. iii. 1876—1877. 



8. Hoffmann, C. K. Zur Anatomie u. Ontogenie von Malacobdella. 

 Niederl. Arch. Zool. Bd. iv. 1877—1878. 



9. Hubrecht, a. a. W. Proeve eener ontwickelungsgeschiedenis van 

 Lineus obscurus Barrois : Prys verhandeling met goud bekroond en 

 uitgegeven door het provinciaal Utrechtsch genootschap van Kunsten en 

 Wetenschapen. Utrecht. 1885. (Only the two following commimica- 

 tions of this author, which treat of the same subject, were accessible to 

 us.) 



10. Hubrecht, A. A. W. Contributions to the Embryology of the 

 Nemertea. Quart. Jour. Micr. Sci. Vol. xxvi. 1886. 



11. Hubrecht, A. A. W. Zur Embryologie der Nemertinen. Zool. 

 Anzeiger. Jahrg. viii. 1885. 



12. Hubrecht, A. A. W. On the Ancestral Form of the Chordata. 

 Quart. Jour. Micr. Sci. Vol. xxiii. 1888. 



