i6o Journal of Comparative Neurology. 



mentary) ; somite, van Wijhe's 7th (myotome, first myotome of 

 lateral trunk musculature in Squalus) ; visceral cleft, fourth; vis- 

 ceral arcJi, fifth ; aortic arch, fifth. 



Metamere IX. Neuromere, neuromere IX ; dorsal nave, 

 rudimentary (unites with vagus in Squalus) ; ventral netve, hy- 

 poglossus, second root ; somite, van Wijhe's 8th (forms first 

 segment of hypoglossus musculature) ; visceral cleft, fifth; vis- 

 ceral arch, sixth ; aortic arch, sixth. 



Metamere X. Neuromere, neuromere X ; dorsal nerve, 

 first spinal (represented by a rudimentary ganglion in Squalus 

 embryos) ; ventral neri'e, hypoglossus ; viscer-al cleft, sixth ; vis- 

 ceral arcJi, seventh ; aortic arch, seventh. 



Metamere XI. Neuromere, neuromere XI ; dorsal nerve, 

 second spinal (rudimentary ganglion in Squalus embryos); veii- 

 tral nen'c, hypoglossus ; somite, van Wijhe's 9th ; visccr-al cleft, 

 seventh ; visceral arch, eighth ; aortic arch, eighth. 



List of Some of the More Important Papers Bearing on the 

 Head Problem. 



Ahlborn, F. 



'84. Ueber die Segmentation des Wirbelthierkorpers. Zeitschr. f. Wiss. 

 Zo5l., Bd. 40, pp. 309-337. 



Balfour, F. M. 



'78. A Monograph on the Development of Elasmobranch Fishes. London, 

 XI -|- 295 pp. 20 plates. 



Beard, J. 



'85. The System of Branchial Sense Organs and their Associated Ganglia 

 in Ichthyopsida. A Contribution the Ancestral History of Vertebrates. Quart. 

 Jour. Micr. Sci., Vol. 26, pp. 95-156, Plates 8-10. 

 DOHRN, A. 



'75. Der Ursprung der Wirbelthiere und das Pnncip das Functionswechsels 

 Genealogische Skizzen. Leipzig, XV -j- S7 pp. 



Froriep, a. 



'92. Entwickelungsgeschichte des Kopfes. Anat. Hefte, Abth. 2, Ergeb- 

 nisse Anat. u. Entwg., Bd. i, pp. 55I-605. 



FUERBRINGER, M. 



'97. Ueber die Spino-occipitalen Nerven der Selachier und Ilolocephalen 



