THE DEVELOPMENT OF THE VENTRAL NERVES IN SELACHII. 307 



3. The " germinative cells" of His are simply mitotic cells. 



4. No neuroblasts migrate from the wall of the neural tube. Their migration 

 is entirely within the wall and is the passive result of the multiplication of cells near 

 the lumen of the tube. 



5. Neuraxones of spinal ventral nerves are formed exclusively by medullary 

 cells. 



6. The cells of ventral nerves are not concerned with the formation of neu- 

 raxones. They form the neurilemma and possibly also in part the connective tissue 

 sheaths of the nerves. Mesenchymatous cells also probably contribute to the forma- 

 tion of the neurilemma and connective-tissue sheaths. 



7. The cells of the forming ventral nerve are migrant medullary elements, 

 to which are later added cells from the adjacent mesenchyme. 



8. The first connection of ventral nerve and myotome is not an intimate neuro- 

 muscular attachment. There is no primary cellular connection such as has been 

 postulated by Sedgwick ('94). 



V. BIBLIOGRAPHY. 



Apathy, S. 



'89-'90. Nach welcher Richtung hin soil die Nervenlehre reformirt werden? Biol. Centralbl., Bd. 9, 



No. 17, pp. 527-538; No. 19, pp. 600-608; No. 20-21, pp. 625-648. 

 Balfour, F. M. 



'81. A Treatise on Comparative Embryology, vol. 2. London, 8, xi+655 + xxii pp. 

 Bardeen, C. R. 



'98. The Development of the Musculature of the Body-wall in the Pig, including its Histogenesis and its 

 Relations to the Myotomes and to the Skeletal and Nervous Apparatus. Johns Hopkins Hospital 

 Reports, vol. 9, pp. 367-399, 10 pis. 



Barker, L. F. 



'99. The Nervous System and its Constituent Neurones. New York, 8, xxxii + 1122 pp., 2 pis. 



Beard, J. 



'92. The Histogenesis of Nerve. Anat. Anz., Bd. 7, No. 9-10, pp. 290-302. 



Beard, J. 



'96. The History of a Transient Nervous Apparatus in certain Ichthyopsida. Zool. Jahrb., Abt. f. Anat., 

 Bd. 9, Heft 2, pp. 319-426, Taf. 22-29. 



Bfraneck, E. 



'87. Etude sur les replis me'dullaires du poulct. Recueil Zool. Suisse. torn. 4, no. 3, pp. 305-364, pi. 14. 



Capobianco, F. 



:00. Delia prima genesi delle cellule nervose della midolla e dei ganglii spinali. Anat. Anz., Bd. 18, Ergan- 



zungsheft, pp. 213-214. 

 Capobionco, F., e Fragnito, O. 



'98. Nuove richerche su la genesi et i rapporti mutui degli elementi nervosi e nervoglici. Ann. neurol. 



Milano, fasc. 2-3, 40 pp., 3 tav. 

 Chiarugi, G. 



'94. ho sviluppo dei nervi oculomotore e trigemello. Nota preliminare. Monit. zool. ital., anno 5, no. 

 12, pp. 275-280. 



