THE CLUPEOID CRANIUM AND THE SWIMBLADDER 447 



An interesting structure which was entire!}' overlooked by all 

 previous investigators except Weber, is a septum which divides 

 the cavity of the anterior bony capsule into two unequal chambers, 

 the inferior of which contains the membranous vesicle of the 

 swimbladder. Tysowski describes this septum as a "fibrose, 

 stark elastische Membran, deren deutlich langs verlaufende 

 Fasern aus sonderbaren Kanalchen in der Knochenwand der 

 Kapsel hervorzugehen scheinen." The periosteum from the in- 

 side of each chamber is reflected on to the corresponding surface 

 of the septum. 



To de Beaufort ('09) we are indebted for a comprehensive 

 investigation of the swimbladder in the Malacopterygii. Of 

 these fishes, the following genera present the clupeoid type of 

 relation between the- labyrinth and swimbladder: Clupea, Pel- 

 lona, Opisthonema, Sardinella, Chatoessus, Engraulis, Dussu- 

 miera, Spratelloides, Coilia, and Chirocentrus. In this group, 

 Pellona is the only genus in which the ear-swimbladder mechan- 

 ism differs from the clupeoid type in any important details. 



By applying modern technique, he was able to demonstrate 

 definitely the non-existence of the utricular diverticulum ex- 

 tending into the anterior bony bulla (as described by Weber 

 and Ridewood). He states that in sections the forward part of 

 the utriculus with the macula acustica rests upon the opening 

 of the bulla "davon durch den perilymphatische Raum getrennt 

 wird." This relation showed in all his sections, both of older 

 larvae and of young fishes. He also denies positively any direct 

 connection between the two utriculi. The subcerebral canal is 

 only a perilymphatic space. With regard to the supracerebral 

 canal, he says: "Ich darf jedoch mit Bestimmtheit erklaren, 

 dass auch diese Verbindung nicht besteht, ebensowenig wie von 

 Hasse beschriebene Verbindung des beiden Duoti endolympha- 

 tica." 



Although de Beaufort adds little to our previous conceptions, 

 he was the first to have a view of the structure of the Clupeoids 

 and allied forms comprehensive enough to discuss the com- 

 parative anatomy of the clupeoid type of the ear-swimbladder 

 relation. His discussion need not be repeated here, but we 



