THE FROG 73 



oviducal funnels, into which they are taken. They then pass along 

 the oviduct, where they are coated with albuminous matter, to be 

 stored in the ovisac until they are finally laid. All these parts of 

 the female reproductive system are subject to variations at different 

 times of the yeai. During the summer they are smallest, but the 

 fat bodies enlarge. In winter, and particularly in the early months of 

 the year, the ovaries enlarge very markedly, while the fat bodies 

 begin to dwindle in size, yielding up their food store to the ovaries 

 to enable them to produce an enormous number of eggs. Shortly 

 after the glandular portions of the oviducts begin to increase in size, 

 their glands becoming active and preparing the albuminous matter 

 with which the egg is surrounded as it passes down the ducts. Finally, 

 in early spring the ova are discharged and stored in the ovisac, so 

 that the ovary diminishes markedly, and the ovisacs become greatly 

 distended with the waiting eggs. After the eggs are laid the various 

 organs all become smaller again. 



The primary male organs are the testes, a pair of yellowish 

 white oval bodies, lying immediately ventral to the kidneys, and 

 suspended in folds of the peritoneum often deeply pigmented, known 

 as the mesorchia. To their front ends are attached corpora adiposa, 

 similar in all respects to those of the female. Each testis is connected 

 to the corresponding kidney by ten or a dozen fine white tubes, the 

 vasa efferentia, running through the mesorchium. The spermatozoa 

 produced in the testes are not discharged into the body cavity, as 

 are the ova from the ovary, but are conveyed to the kidney by the 

 vasa efferentia. The kidneys resemble those of the female, and have 

 ureters arising from their lateral edges. The ureter serves also to 

 convey the spermatozoa to the cloaca, and so functions as a sperm 

 duct or vas deferens. Between kidney and cloaca the vas deferens 

 gives off laterally a sac-like dilatation, the vesicula seminalis, in which 

 the sperms are stored until required. Thus there are only three 

 pores leading into the cloaca of the male : a pair of uro-genital openings 

 situated on papillae on its dorsal wall, and the single opening of the 

 urinary bladder on the ventral wall opposite. The various parts of, 

 the male system, i.e. fat bodies, testes, and vesiculae seminales, also 

 vary in size at different times of the year, but not to such a marked 

 degree as the female organs. 



A section of the ovary shows it to consist of a hollow sac 

 with folded walls, from which a number of partitions pass inwards. 

 From the walls and partitions the eggs project towards the interior. 

 The ovum or female reproductive cell itself is a spherical cell, varying 

 in size according to its stage of development, with a large vesicular 

 nucleus situated eccentrically and containing several distinct nucleoli. 

 The cytoplasm of the egg is extremely granular, owing to the presence 



