190 



ZOOLOGY. 



papilla, into the dorsal side of the cloaca. In the male 

 this is the urogenital sinus already mentioned : in the 

 female, it is called the Uinary_^in.us. There is no trace of 

 the ventral urinary bladder of frog and rabbit. 



20. The " Ductless Glands." The spleen consists of a 



large portion 

 attached to 

 the apex of 

 the stomach, 

 and of a long, 

 narrow strip 

 along the 

 distal limb of 

 the stomach. 

 The thyroid 

 lies just 

 ventral to 

 the basi- 

 hyal, and 

 laps under 

 the front 

 end of the 

 truncus ar- 

 teriosus. It 

 forms a good 

 landmark in 

 dissection for 

 the front pair 

 of afferent 

 branchial 



Pig. 101. MALE REPRODUCTIVE GROANS OF DOGFISH. 

 (Slightly diagrammatic.) 



vessels. 



Thetkymus 

 lies on the 



dorsal side of the gill-arches, near the anterior cardinal sinus. 

 There is a pair of adrenals, and a median inter-renal body 

 which are together homologous with the adrenals of the 

 rabbit. 



21. Classification. Several species of Scyllinm are 



