450 



HENRY C. TRACY 



The relations of the anterior part of the organ are somewhat 

 different. As it passes over the pericardial cavity, it comes to 

 He between the kidneys of the two sides. Here the intercostal 

 aponeurosis sends off two strong layers, one of which runs 

 ventral to the swimbladder and the other dorsal to it; each 

 connects with the corresponding layer of the other side. This 



Fig. a Drawing to show relations of the anterior end of the swimbladder and 

 the cartilage canals containing the precoelomic diverticulum and its branches 

 (Alosa sapidissima). The structures are shown from the ventral side and in 

 cross-section. Semidiagrammatic. Abbreviations on page 473. 



part of the organ, then, is enclosed in an aponeurotic sheath of 

 nearly tubular form, which runs anteriorly and attaches itself 

 to the cartilage tube which encloses the precoelomic diverticu- 

 lum (fig. a). The intercostal aponeurosis itself continues cepha- 

 lad, to clothe the ventral surface of the musculature covering 

 the occipital and basilar parts of the skull; other extensions of 

 it pass dorsally to be attached to the vertebral column. 



The precoelomic diverticulum is a tubular prolongation of the 

 tunica interna of the swimbladder. There is some variation in 



