58 



THE VERTEBRATE OVARY AND ITS RELATIONSHIP TO REPRODUCTION 



ROCE SS 

 MUSCLE 



RIAN SINU S 



IRI 4N OR TAIL COE LOM 



Fig. 28. Dissection of female specimen of the common flounder, Limanda jerruginea. 

 It particularly shows the ovary with its laterally placed ovarian sinus. Observe that the 

 ovary, during the breeding season, is an elongated structure which extends backward into 

 the tail. There are two ovaries, one on either side of the hemal processes of the caudal 

 vertebrae. 



Its shape, also, is most variable in different species. In mammals it is a 

 flattened ovoid structure in the resting condition, but during the reproductive 

 phase it may assume a rounded appearance, containing mound-like protrusions. 

 In birds and reptiles it has the general form of a bunch of grapes. In the 

 amphibia it may be composed of a series of lobes, each of which is a mass 

 of eggs during the breeding season, and in teleost and ganoid fishes it is 

 an elongated structure extending over a considerable area of the body. 



Regardless of their many shapes and sizes, the ovaries of vertebrates may 

 be divided morphologically into two main types, namely, compact and saccular 

 forms. The compact type of ovary is foimd in teleost, elasmobranch, cyclo- 

 stome, ganoid, and dipnoan fishes, as well as in reptiles, birds and mammals. 

 It has the following regions (figs. 30, 31 ): 



( 1 ) the medulla, an inner zone containing relatively large blood and lymph 

 vessels; 



(2) the cortex, an area outside of and surrounding the medulla (except 

 at the hilus), containing many ova in various stages of development; 



(3) a tunica albuginea or connective-tissue layer surrounding the cortex; 

 and 



(4) the germinal epithelium or the covering epithelium of the ovary. 



The germinal epithelium is continuous with the mesovarium, the peritoneal 

 support of the ovary, and the particular area where the mesovarium attaches 

 to the ovary is known as the hilus. Within the mesovarium and passing 



