Fig. 12. Transverse section taken .35 mm. caudad of Fig. 11 as seen from 

 the rear (caudad). Left lateral trunk emptying into the left sinus (x), and 

 the dorsal trunk crossing the left side of the vertebral column preparatory 

 to emptying into the left sinus (x). The right haemal trunk terminates in 

 the right sinus (x) .06 mm. caudad of this section, while the right lateral 

 trunk does not join the right sinus (x) until a point .45 mm. caudad of this 

 section is reached. X ^■ 



Fig. 13. Is from a section .22 mm. caudad of Fig. 12 viewed from the rear 

 (caudad) ; dorsal trunk terminating in the left sinus (x) ; caudal artery and 

 vein, ventral trunk and sinuses (x) seen in cross section, x 9. 



Fig. 14. A transverse section .05 mm. caudad of Fig. 13 as seen from the 

 rear (caudad) ; last neural vein crossing the left sinus (x) and emptying into 

 the caudal vein. The caudal artery has bifurcated, and its two forks, 

 together with the caudal vein, the ventral trunk and the two sinuses (x) are 

 seen in section. X 9. 



Fig. 15. Taken from a transverse section 23 mm. caudad of Fig. 14 ex- 

 amined from the rear (caudad). The two caudal sinuses «'ve seen In section 

 emptying into the caudal vein. Both caudal arteries, both sinuses (x), the 

 last neural vein and the ventral trunk are also shown in section, x '•^■ 



Fig. 16. From a transverse section .43 mm. caudad of Fig. 15 viewed from 

 the rear (caudad). The left sinus (x) is seen in section terminating in the 

 left caudal sinus, but the right sinus (x) does not empty into the right caudal 

 sinus till a section .09 mm. caudad is reached. The caudal vein is bearing 

 off to the left. Both caudal arteries, the right sinus (x) and the ventral 

 trunk are seen in section, x 9- 



Fig. 17. A transverse section .67 mm. caudad of Fig. 16 as seen from the 

 rear (caudad). The right caudal sinus communicates mesad with the left 

 through the canal (o). The two arteries and caudal vein are seen in section, 

 and the ventral trunk is traveling dorsad in the basal canal of the caudal 

 fin to become the caudal trunk (C. T.). x 9- 



