' EGGS AND TADPOLES 9 



the pad on the hand, but by the swollen condition of the 

 trunk, due to the interior being distended with eggs. After 

 a time the eggs are laid, being passed out of the vent by 

 hundreds ; each is a little globular body about j^jth inch in 

 diameter, half black and half white, and surrounded by a 

 sphere of clear jelly, by means of which the eggs adhere 

 together in large irregular masses, the well-known " frog- 

 spawn." As the eggs are laid the male passes out of his 

 body, also by the vent, a milky fluid, the milt or spermatic 

 tlmd, which gets access to the eggs and impregnates or 

 fertilises them. Without impregnation they are incapable 

 of developing. 



Neither male nor female takes the slightest care of the 

 eggs when once they are deposited and fertilised. They 

 are simply left in the water unprotected in any way ; and, 

 naturally enough, the mortality among them during the 

 course of development is very great, the majority being 

 eaten or otherwise destroyed, and only a very small per- 

 centage coming to maturity. 



The first noticeable change in the spawn is that the 

 sphere of jelly surrounding each egg swells up so as to 

 acquire several times the diameter of the enclosed egg. 

 The egg itself, or e?nbryo, as it must now be called, 

 gradually becomes entirely black, then elongates, and takes 

 on the form of a little creature (Fig. i, i), with a large 

 head, a short tail, and no limbs ; which, after wriggling 

 about for a time, escapes from the jelly and fixes itself, by 

 means of a sucker on the under side of its head, to a 

 water-weed. Great numbers of these tadpoles, as the free- 

 living immature young or larvce of the frog are called, may 

 be seen attached in this way. At first they are sluggish and 

 do not feed, but, before long, they begin to swim actively 

 by lashing movements of their tails, and to browse on the 



