CURIOSITIES OF EVOLUTION. 



7^5 



tiles, and birds, and constituting the uterus and Fallopian tubes in 

 mammals. In their earliest stage they are known as the prone- 

 pliros, or " head-kidney/' and answer to the permanent condition 

 of the renal organs in worms; in their second stage they are 

 known as the " ducts of Miiller." 



The second set of tubules constitute the mesonepliros or 

 Wolffian bodies ; they act for a time as kidneys, and then become 



Fig. 1.— Pineal Ete in Hatteria. A, nerve ; B, blood-vessel ; C, retina ; D, greatly elongated 



rods and cones of retina. 



the ducts of the generative organs in the male. In the female 

 they have no later functions, but their atrophied remains per- 

 sist, and give rise to various forms of cystic disease. The upper 

 division of the Wolffian duct, with its tubes, can be found lying 

 above the ovaries, and is known as the parovarium. It is fre- 

 quently the seat of degenerative disease, not only in human 

 beings, but in lionesses, tigresses, and cows. The middle portion 

 often disappears, but in the cow the whole tube persists, useless 

 always, and mischievous very frequently. Both sets of tubules, 

 those of the pronephros and those of the mesonephros, or, in 

 other words, the ducts of Miiller and the Wolffian ducts, persist 

 throughout life in both males and females, one set becoming 



VOL. XXXIII. — 50 



