PLATE XIII. 



Fig. 1. Transverse section of the right ovary of a young Common Sole, 7^ inches long, 

 killed May 2, 1889 ; magnified 45 times, linear. 



f.e. fibrous tissues forming the wall of the ovary. 

 o.g. ovigerous lamellae. 

 b.v. blood-vessels, ovarian artery and vein. 



Fig. 2. Portion of an ovigerous lamella from transverse section of an ovary of a Sole 

 10J inches long, killed January 28, 1889 ; magnified 450 times. 



g.e. germinal epithelium. 

 o. ova. 



Fig. 3. Section of an ovum approaching maturity, from the ovary of a Sole killed 

 when spawning was almost finished, on April 11, 1889 ; magnified 70 times. 



b.v. blood-vessels. 

 f.e. follicular epithelium. 

 f.m. follicular membrane. 

 v.m. vitelline membrane. 



Fig. 4. Transverse section of the right testis of a Sole 9 inches long, immature ; 



magnified 45 times. 



f.e. fibrous envelope. 



r.t. radial testicular tubes. 



l.t. longitudinal testicular tubes. 



Fig. 5. Closed end of one of the radial testicular tubes shown in Fig. 4 ; magnified 450 



times. 



f.e. fibrous envelope. 



g.e. male germinal epithelium. 



Fig. 5a. Longitudinal portion of a testicular tube from the same section cut 

 transversely, containing spermatoblasts and ripe spermatozoa ; magnified 

 450 times. 



Fig. 6. Transverse section of the cord containing the testicular ducts from an adult 

 male Sole killed in the breeding season, March 23, 1889; magnified 70 

 times. 



f.t. fibrous tissue. 



l.t. the testicular ducts. 



u.l). urinary bladder lined by an epithelium. 



Fig. 7. Spermatozoon of Dab (Pleuronectes limanJa) ; magnified 500 times. 



