DEVELOPMENT OF THE NERVOUS SYSTEM. 73 



Front edge of anterior fin (18 mm. embryo) ... 4 to trunk segment 9 

 Bark edge ... 14 i 7 



Cloaca ...44-48 4 8- 49 



Anterior end of coelom. from occipital segment, 3 n 



DEMONSTRATION OR LABORATORY WORK. 



1. Study the development of the neural plate, neural tube and 

 brain in embryos of the salamander, a selachian, pig or chick. 



2. In the same material study the neural crest and the formation of 

 the spinal and cranial ganglia. 



3. Study the dorso-lateral and epibranchial placodes and the develop- 

 ment of the auditory and lateral line organs, eye and olfactory organ. 



4. Study the relations of the chorda, the anterior end of the ento- 

 derm and mesoderm, hypophysis and olfactory pit and neuropore in 

 selachian or salamander embryos. 



5. Notice the neuro meres in the hindbrain of any embryos and 

 look for the shifting in position of the auditory vesicle and the trigem- 

 inus and other nerve roots. 



6. In any selachians or cyclostomes that are available make careful 

 dissections of the nerves in the spino-occipital region, noting the num- 

 ber of dorsal and ventral roots present and their position relative to the 

 vagus and glossopharyngeus. The smaller nerve roots can be brought 

 to view by painting the surface of the brain with i or 2 per cent. 

 osmium solution, which should be thoroughly w r ashed away with water 

 as soon as the nerves are blackened. 



7. Study the formation of the neuroblasts in the central nervous 

 system and the growth of central and peripheral processes from the 

 sensory ganglion cells. This can be done well in amphibian embryos 

 stained with haemalum and acid fuchsin. 



LITERATURE. 



Bardeen, C. R.: The Bimeric Distribution of the Spinal Nerves in Elas- 

 mobranchii and Urodela. Amer. Jour, of Anat, Vol. 3. 1904. 



Brauer, A.: Beitrage zur Kenntniss der Entwickelung und Anatomic der 

 Gymnophionen. Zool. Jahrb., Suppl. 7, 1904. 



Braus, Herman: Beitrage zur Entwickelung der Muskulatur und des 

 peripherischen N ervensystems der Selachier. Morph. Jahrb., Bd. 27, 1899. 



Carpenter, F. W.: The Development of the Oculomotor Nerve, the Ciliary 

 ganglion, and the Abducent Nerve in the Chick. Bull. Mus. Comp. Zool. 

 Harvard College, No. 172. 1906. 



Disse. T.: Riechschleimhaut und Riechnerv beiden Wirbelthieren. Merkel 

 u. Bonnet's Ergebnisse. Bd. n. 1901. 



