22 AYERS. [Vol. VI. 



utricular chamber cephalad of the median Hne as a tubular evag- 

 ination from the lower, posterior lateral face, deep within the 

 utriculo-saccular groove, but it is much less a median structure 

 than the saccular duct which leaves the utriculo-saccular cham- 

 ber almost immediately from the line of union of the two 

 chambers. Both ducts run upwards (and near each other in so 

 doing), inwards, and backwards, piercing the cranial wall side 

 by side, and end projecting into the subdural lymph space. 

 The foramen giving passage to these ducts lies above and is 

 entirely unconnected with the large foramen for the passage of 

 the auditory nerve. It is much smaller and is nearly filled by 

 the two tubes, the remaining space being occupied by the peri- 

 lymphatic tissue. The saccular duct is lined by a pavement 

 epithelium throughout, except where the sense organ furnishes 

 a columnar epithelium. 



The importance of this question has led me to search for the 

 second duct among the Gnathostomes, and if one can rely on 

 the literature of the subject, two endolymphatic ducts are pres- 

 ent in some of the Elasmobranch fishes. 



Hasse found (and in this he agrees with Ibsen) a bifurcated 

 endolymphatic duct, the main branch of which arose from the 

 inner wall of the sac, while the small branch arose from the 

 upper inner wall of the Recessus utriculi and opened into 

 the larger tube. Hasse, however, was in error in regard to the 

 extent of the tube. 



I have not seen the bifurcate endolymphatic duct, described 

 by Hasse for the species which he studied, but the two endolym- 

 phatic tubes observed by E. H. Weber, I have found beautifully 

 developed in Sphyrna zygaena, and there is not the slightest 

 doubt as to their occurrence.^ Although I have never found 

 two open endolymphatic ducts, except in the Hammer-head 

 Shark, I have frequently found in the place one would seek for a 

 second tube, a rod, apparently solid, reaching from the sacculus 



1 Breschet (40, 1838) describes the main facts about the endolymphatic ducts as 

 observed by him in the following words : " Sur la cote interne du bulbe auditif, on 

 voit deux cavites dirigees de haut en bas at recourbees en arriere vers leur extremites. 

 Ces conduits se retrecissent pres de la peau exterieure et semblent 8tre bouchees en 

 cet endroit par du tissu cellulaire; ils aboutissent a la partie moyenne et superieure 

 de la tete ou ils s'ouvrent par deux petits orifices." 



"Dans le milandre (^Squaiilus galetis, Z.), il y a ce qu'on nomme improprement 

 des events : ceux-ci s'ouvrent par des petits orifices sur la tete, pres de la ligne mediane 



