284 Journal of Comparative Neurology and Psychology. 



Frosches." Fig. i a is a lateral view of the labyrinth organs; 

 Fig. I B a median view. These figures together represent clearly 

 the important sensory portions of the ear of the frog. Since 

 there is no organ of Corti, whatever ability to hear the animals 

 may possess must be due to the functioning of some portion 

 of the membranous labyrinth. 



Figure 3 is presented for the purpose of showing the strik- 

 ing difference in the size of the tympanum of male and female 

 green frogs. The individual on the right is a male, that on 

 the left a female. Although these two frogs were of the same 

 length and weight the maximum diameter of the tympanum in 



ccnZymp 



O^d 



^efixft/ 



Fig. 2. Transverse section of the head of the frog to show the relations of 

 the various parts of the ear (diagrammatic), tymp. memb., tympanic membrane; 

 col., columella; stp., stapes ; memb. lab., membranous labyrinth ; Nv. VIII., au- 

 ditory nerve; med. obi., medulla oblongata ; ch.plx., choroid plexus; tymp. cav., 

 tympanic cavity \fen. ov., fenestra ovalis ; buc. cav., buccal cavity ; eus.i.. Eusta- 

 chian tube ; an. tymp., annulus tympanicus ; b. hy., body of hyoid ; o. st., epi- 

 sternum ; mnd., mandible ; //f., pterygoid ; qu.ju., quadrato-jugal. From Par- 

 ker and Haswell. 



the male is one-third greater than that in the female. Measure- 

 ments of several other individuals yielded the following results. 

 For ten males whose average length was 7.31 cm. the average 

 maximum diameter of the tympanum was 8.15 mm. ; for ten 

 females 6.52 cm. in length it was 5.99 mm. Or if we compare 

 individuals of like size: for a male 6.2 cm. the diameter was 

 6.3 mm. in contrast with 5.0 mm. for a female of the same 



