EAR-SWIMBLADDER RELATION IN CLUPEOIDS 229 



A similar canal short but of larger diameter, connects the 

 loose tissue on the mesial surfaces of the two sacculi. This 

 saccular subcerebral canal has previously been mentioned only 

 by Tysowski. 



The supracerebral canal is a space in the hollow band of 

 compact tissue which arches over the medulla behind the cere- 

 bellum (fig. 16). As this passes down posterior to the superior 

 sinus of the utriculus, it divides (figs. 4, 5, 6, and 7; PSCM, 

 PSCL) ; one banch passes through the compact perilabyrinthine 

 tissue mesial to the sinus and connects with spaces mesial to 

 the sacculus, the other gradually passes behind and then lateral 

 to the sinus and connects with the lateral spaces above men- 

 tioned. This branching of the supracerebral canal may per- 

 haps explain the conflicting views of Breschet and Hasse. 

 Breschet must have seen merely that part of the supracerebral 

 canal which passes between the two superior sinuses; Hasse 

 doubtless traced the branch of the canal which passes down to 

 the sacculus mesial to the sinus and assumed it to be the endo- 

 lymphatic duct. 



The upper chamber of the anterior osseous capsule contains 

 only a very sparse connective tissue. It is apparently very 

 similar in structure to the perilabyrinthine spaces. It will be 

 observed, therefore, that only a very loose and rarefied con- 

 nective tissue intervenes between the elastic septum of the 

 osseous capsule and the thin part of the utricular wall which 

 bridges the fenestra and connects the anterior and middle 

 divisions of the macula. 



THE MEMBRANOUS LABYRINTH 



The form and structure of the membranous labyrinth of the 

 Clupeoids appear on dissection quite different from those of 

 other teleosts, because the thickenings of the compact tissue, 

 as described above, do not conform externally to the shape of 

 the utriculus and sacculus. Nevertheless, the epithelial part 

 of the labyrinth is essentially like the teleostean labyrinth in gen- 

 eral except in the form of the recessus utriculi and the structure 

 of the macula acustica utriculi. 



