14 FROGS. 



DEVELOPMENT AND TRANSFORMATION. 



The eggs hatch in from 3 or 4 to 25 days, dependmg on the tem- 

 perature conditions. At hatching, the larvae have a distinct neck, 

 with a prominent head and body. The tail is very small or absent. 

 On the ventral side of the head is an invagination or depression 

 which is to be the mouth. Behind this comes the ventral adhesive 

 disk or disks, which help the little creature to attach itself to the egg 

 mass or to hang itself upon some plants. In front of the mouth are 

 two deep, dark pits which later become the nostrils. On either side 

 of the head appear swellings wliich become the external gills. The 

 eyes do not yet appear. 



As development goes on the external gills appear as branched 

 organs, two or tln-ee on a side; the eye shows as a ring beneath the 

 skin; and the tail grows and presents a middle muscular portion 

 where the muscle segments clearly show. This middle part supports 

 a thin, waferlike tail tin the parts of which are called, respectively, the 

 lower and upper crests. The nasal pit shifts in position and becomes 

 the nostril, and the vent opens. The mouth appears, and dependence 

 on the yolk of the belly ceases. Soon the external gills begin to dis- 

 appear, a lateral flap or fold of skin connects the head with the body, 

 and the neck region disappears. Beneath this fold internal gills 

 develop. On the left side, the lateral flap does not close completely, 

 but leaves an opening, the spiracle. The water passes into the mouth 

 over the internal gills and out this hole on the left side. On the 

 mouth a membranous, frmged lip, with upper and lower portion, 

 comes into bemg. At the portal are homy jaws or mandibles. On 

 the upper and lower portions are rows of horny teeth. The eye is 

 no longer a covered pigmented ring, but is now at the surface. The 

 intestine has become much elongated and coiled. The buds of the 

 hind limbs begin to appear. The fore limbs start to develop beneath 

 the skin. When the hind limbs have reached considerable size the 

 left arm comes out through the spiracle and the right arm breaks 

 through the skin. , 



The process of transformation is now on. The tail crests decrease 

 in size, and the creature begins to live on its tail; that is, absorbs it. 

 The gills vanish, and the lungs begin to serve as the sole respiratory 

 organs, if the skin be not considered. The eye assumes eyelids. 

 The tadpole mouth fringe, with its horny jaws and horny teeth, is 

 discarded, and a true frog mouth beghis to appear. The long intes- 

 tine becomes v.^onderfully shortened, and the small frog, with a vestige 

 of a tail, is ready to leave the water. This process is termed tram- 

 formation or metamorphosis. 



SELECTION OF STOCK. 



Most of the inquiries which the Bureau receives center about 

 possible literature concerning frog culture or about the supply of 

 breeding-frog stock, frogs either unmated or mated, eggs, or tadpoles. 

 At the present time no su])ply bureau or hatchery can offer certified 

 eggs or tadpoles of a particular species, and rarely can matqd pairs 

 be supplied. Some of the dealers in zoological supplies and some 

 hatcheries can furnish frogs and might at certain seasons ofl'er to 

 furnish mated pairs. But such, which are paired in captivity, would 



