







PLATE XIX 



8ft .! 



FIG. 73. Diagram of heart, etc., of normal trout embryo 

 (p. 12). Lettering as in Fig. 75. Above s.v. is the 

 common opening of the anterior jugular veins. For 

 general references see under PI. I. fig. i. 



FIG. 74.-- Diagram of the heart, etc., of the double 

 monster (Class III.) illustrated in PI. II. fig. 7, which see 

 for general references. Lettering as in Fig. 75. 



FIG. 75. Diagram of the heart, etc., of a double monster 

 belonging to Class IV., i.e. with union in pectoral region, 

 the adjacent pectoral fins being present but united (p. 19). 



V. Ventricle. 

 An. Auricle. 

 SV. Sinus venosus. 

 >6". Duct of Cuvier. 

 DC'. Inner or adjacent ducts of Cuvier. 

 VJ. Jugular vein. 

 VC. Cardinal vein (posterior). 

 VC'. Inner or adjacent cardinal veins. 





ijou. I 



FIG. 76. Diagram illustiating the Wolffian duct and 

 urinary bladder in a normal trout embryo (p. 12). Letter- 

 ing as in Figs. 77-81. For references see under PI. I. fig. i. 



FlGS. 77-81. Diagrams illustrating the arrangement of 

 the Wolffian ducts and bladders according to the different 

 types described on pp. 21-23. It w '" be noted that the 

 ducts which associate themselves in pairs with the bladders 

 nearly always consist of the right duct of one embryo and 

 the left of the other. Fig. So is an exception, and Fig. 81 

 an example of pure ventral union (p. 23). 

 HL. Bladder. 

 />'/.'. Bladder formed by the inner or adjacent pair of 



Wolffian ducts. 

 WD. Wolffian ducts. 

 WDb, \VDt'. Wolffian ducts belonging to one of the twins in each 



of the figures. 

 \VDa, WDa'. Wolffian ducts belonging to the other twin in each' 



of the figures. 



Int. Intestine. :m 3, 



39, K. Rectum. 



K Vent. 



P. Urinary pore. 



"A. .\H 



i 





