24 Dynamic Theory. 



a number of small branch tubes similar to those described in connection 

 with the primary kidney duct. The ends of these tubes afterwards re- 

 ceive the permanent coiled arteries that pass the blood in and out of the 

 kidneys. The posterior ends of the kidney ducts remain as canals and 

 become the ureters or tubes for conveying the urine into the bladder. 

 At first, the ureters discharge into the cloaca through the primitive kid- 

 ney duct, but later, the connection is with the part of the allantois which 

 remains within the body cavity after the closing of the body wall, and 

 which becomes the permanent urinary bladder. The posterior or lower 

 end only, of the allantois stalk, is used for the bladder, and the remain- 

 ing part between the bladder and the navel remains .shriveled up into a 

 solid cord called the urachus, no longer of any use. The urinary blad- 

 der, at first, of course, opens into the intestine where the allantois was 

 joined to the intestine, but later, in the higher mammals, a transverse 

 partition is formed, separating the urinal exit from the body from the 

 intestinal exit. 



M FIG. 30. Diagram of repro- 

 ductive organs. 



Middle fig. is general plan 

 of reproductive organs. Left 

 hand is female, and right is 

 male derivative. 



Cl. Cloaca. R. Rectum. 

 Bl.-Urinary bladder. U. 

 Ureter. K. Kidney. Uh. 

 Urethra. G. Genital gland 

 ovary or testis. W. Wolf- 

 fian body. Wd. WolfBan 

 duct. M.-Miillerian duct. Pst. 

 Prostate gland. Cp. Cow- 

 pers gland. Csp. Corpus 

 spongiosmn. Cc. C o r p u s 

 cavernosum. In female. V. 

 Vagina. Ut. Uterus. Fp. 

 Fallopian tube. Gt. Gaert- 

 ners duct. W, Wd. Becomes 

 parovarium. A. Anus. Cc, 

 Csp. Clitoris. In the male. 

 Cap, Cc. Penis. Ut. Mas- 

 culine uterus. Vs. Vesicula 

 seminalis. Vd. Vas deferens. 

 FIG. 30. (Huxley.) 



Ins%de of and a little below the primitive kidneys are formed the 

 germ glands or organs for the production of the egg cells. These 

 glands originate from the boundary line or place of junction of the two 

 primary germ layers, where they originally unite to form the middle 

 layer of the embryo sfteld, near the place from which the primitive kid- 

 neys were originally differentiated. These spots necessarily keep near 

 the kidneys as they are gradually pressed to the body cavity by the 

 formations outside of them. 



At an early period of embryonic development, each of the wolffian 



