AMPHIBIA. 



207 



Oct. 1 



which largely make up the epithelial lining of the seminiferous 

 tubules. Each sperm-mother-cell originates a tuft of sperms, an 

 unused stump (sperm-blastophor) being left over. 



Female Reproductive Organs (Fig. 60). The ovaries are two 

 flattened sacs, varying much in size according to the season, and 

 situated similarly to the spermaries. The pleuro-peritoneum 

 invests each of them and forms a double suspensory fold, the 

 mesovarium. Ova, of various sizes, enclosed in follicles, project 

 on the outer surface of the ovary. The oviducts are two much- 

 coiled tubes invested in pleuro-peritoneum, and each with a 

 narrow anterior end opening near the 

 root of the lungs by a ciliated funnel. 

 The two funnels are close together 

 (the organs in the Fig. have been taken out 

 of the body), and open into a common 

 ciliated depression. The oviducts widen 

 behind, and each of them finally dilates 

 into a thin-walled uterus, opening on a 

 prominent papilla on the dorsal wall of 

 the cloaca. The two papillae are situated 

 close together, just in front of the 

 urinary apertures. 



The ovary contains numerous ova 

 enclosed in follicles, by the rupture of 

 which they escape into the body-cavity. 

 The mature ovum is about T V of an inch 

 in diameter. It is covered by a delicate 

 mielline membrane, and possesses gran- 

 ular pigmented vitellus, and a large 

 germinal vesicle with numerous germinal 

 spots. Two polar cells are formed before 

 fertilization. 



The wall of the oviduct contains 



Fig. 60. FEMALE REPRO- 

 DUCTIVE ORGANS OF FROG 

 (after Ecker and Wieder- 

 sheim). Right ovary re- 

 moved. ov, Left ovary; 

 od, oviduct; od', funnel 

 of ditto; ut, uterus; ut', 

 opening of ditto in cloaca ; 

 , kidneys; u,u, openings 

 of ureters ; cl, cloaca. 



numerous branched tubular glands 

 which secrete a glairy substance, cap- 

 able of swelling up immensely by 

 imbibition of water. The wall of the uterus contains numerous 

 unstriated muscle-fibres. 



At the commencement of the breeding-season (early spring for 

 R. temporaria), the males affix themselves to the backs of the 



