743 



The presence of' tlie fenestra in the einbrj'O is in anj' case a 

 snpport to the old tlieory, which in later years lias frequently been 

 attacked, the theory namely: that the stapes in higher animals is 

 homologous to the hyomandibular in tishes. 



INDEX LETTERS. 



Csi. Caiialis seraicircularis lateralis. 



Csp. Cart, spiracularis. Each of the two spirauular cartilages (fig. 2a) is sectioned 



twice. 

 E. Top of the epibranchial of the first branchial arch. 

 Ep. Epithelial body. 

 Fv. Fenestra vestibuli (ovalisi. 

 Hm. Hyomandibular. 

 Kci. .Second branchial clel't. 

 Prj. Palatoquadrate. 

 Ro. Regie olica of the skull. 

 So. Spiracular sense organ. 

 Th. Thvmus. 

 Vj. Vena jugularis. 



LITERATURE. 



"'Agar, W. E. The Spiracular Gill (Heft in Lepidosiren and Protopterus. Anal. 



Anzeiger, Bd. 28, 1906. 

 •^Allis Jr. E. Phelps. Thp Lateral Sensory ('anals, the Eye Muscles and the 



Peripheral Distribution of certain of the Cranial Nerves of Mustelus laevis. Quart. 



Journ. of niicr Science, Vol. 45, 1901. 

 -/ Bemmelen, J. F. VAN, Uebei- vermuthliche rudimentare Kiemenspalten bei Elas- 



mobranchiern. Mitth. a. d. zoologischen Station zu iNeapel, Bd. 6, 1885. 

 *Braus, H. Ueber den einbryonalen Kiemenapparal von Heptanchus. Anatomischer 



Anzeiger, Bd. 29, 1906. 

 \ Bridge. F. W. On the Osteology of Polyodon folium. Phil. Trans. Roy. Soc. 



Vol. 169. 1879. 

 •DoHRN, A. Die Entwicklung and Differenziruug der Kiemenbogen der Selachier. 



Mitth. a d zoologischen Station zu Neapel, Bd. 5, 1884. 

 ^Fritsche, E. Die Entwickelung der Thymus bei Selacliiern. Jenaische Zeitschr. 



f. Naturwiss. Bd. 46, 1910. 

 'GooDRiCF-i, E. S. On the Structure of the Excretory Organs of Amphioxus. Quart. 



Journ. of micr. So. Vol. 54, 1909. 

 \ Greil, a. Entwickelungsgeschichle des Kopfes and des Blutgefassystemes von 



Ceratodus forsteri. Denkschr. d. Mediciniscli Naturwiss. Ges. zu Jena, Bd. 4, 



1913. 

 j^Hammar, J. Aur;. Zur Keiintnis der Elasmobranchier-Thymus. Zool. Jahrbiicher, 



Abt. f. Anat. und Ontog. Bd. 32, 1912. 



