634 



portion of the cochlea in the Reptiles. The older view is the only 

 one that offers any consistent explanation of the facts, and to this 

 I would add my own suggestion as to a kind of competition between 

 lagena and pars basilaris, in which the latter was victorious, owing 

 to its relation to the perilymphatic system and to the "migration" of 

 a portion of its sensory area on to the basilar membrane. 



In conclusion, we may consider very briefly the question as to 

 what significance we are to attach to the transitory macula ductus 

 reunientis. I agree with Dr. Alexander in rejecting any homology 

 between this structure and the macula neglecta. In Lacerta agilis, 

 however, I have found in the pars basilaris a strip of epithelium which 

 I believe to represent the original papilla basilaris of Amphibia, and 

 this can be traced, in the clearest possible manner, into the ductus 

 sacculo-cochlearis. I therefore put forward the suggestion that the 

 macula .ductus reunientis is really a disappearing vestige of a part of 

 the papilla basilaris, of that part which lost its function when the 

 basilar membrane became the chief area of distribution of the sensory 

 epithelium of the pars basilaris. However this may be, we are justified 

 in maintaining that the macula ductus reunientis of the embryo guinea- 

 pig does not correspond to the papilla lagenae of Amphibians, nor the 

 ductus itself to the lagena, but that the latter with its sensory area 

 is the same structure throughout the whole of the Vertebrate series. 



Freiburg i. B., Aug. 1. 



References. 



1) Alexander, Gr., Ueber Entwicklung und Bau der Pars inferior 

 labyrinthi der höheren Säugetiere. Denkschrift d. kgl. Akad. der 

 Wissensch., math.-naturw. Klasse, Bd. 70, 1901. 



2) Hasse, 0., Die vergleichende Morphologie und Histologie des häutigen 

 Gehörorganes der Wirbeltiere. Supp. zu Anatomische Studien, Leip- 

 zig 1873. 



3) Retzius, G., Das Gehörorgan der Wirbeltiere. Stockholm 1881. 



4) Kuhn, Üeber das häutige Labyrinth der Amphibien. Arch. f. mikr. 

 Anat., Bd. 17, 1880. 



5) — , Ueber das häutige Labyrinth der Reptilien. Ebenda, Bd. 20, 1882. 



6) Harrison, H. S., On the perilymphatic spaces of the Amphibian ear. 

 Intern. Monatsschr. f. Anat. u. Physiol., Bd. 19, 1902. 



