DEVELOPMENT OP OVA OP BIRD. 579 



to that of the parent, than we see in any other animals. The 

 appearance of the ovary of the Fowl in process of laying is 

 shown in fig. 314 ; its surface is rendered uneven or knobby 



Fig. 314. OVAHY OF THE FOWL, with ova in various stages of development: 



a, mature ovum within its calyx, which is about to rupture along the non-vascular 

 streak bb; c c, less advanced ova ; d, a calyx from which the ovum has escaped ; 

 e, still younger ova. 



by the protrusion of the ova in various stages of enlargement, 

 those which are most mature (a, c) forming pear-shaped 

 projections which only hang-on by a narrow stalk ; but each 

 ovum is still included within an extension of the fibrous sub- 

 stance of the ovary (fig. 302), termed the calyx, through which 

 blood-vessels are conveyed over its surface ; and when the 

 ovum escapes by the rupture of this, along a line (6) from 

 which the vessels have previously retreated, the calyx remains 

 as an open cup (d). The ovarium of such Mammals as pro- 

 duce several young at once, presents a corresponding appear- 

 ance as each set of ova is approaching maturity ; save that, as 

 the mass of yolk is comparatively small (no "food-yolk" being 

 provided), the ova do not project so much from its surface. 

 In Fishes, on the other hand, we find an enormous number 

 of ova produced at once ; the whole ovarium, when they are 

 approaching maturity, being so crowded with them that its 

 p p 2 



