TAXONOMY, LIFE-HISTORY, AND GENERAL 7 



of the mother and does not leave the vitelline membrane, she con- 

 cludes that the increase in weight is due to the absorption of water. 

 Monsters are not uncommon (cf. Kaufman, 1913; Stadtmiiller, 

 1930, and others). Deposition often occurs at night, and Schreiber 

 (19 1 2) supposes that the act must often be fatal to the females, 

 since he frequently finds dead adults near the water containing 

 young. 



3. The Larvae. 



The larvae are about 25-30 mm. long at birth, of greyish-brown 

 colour dorsally and greyish white ventrally, flecked with arachnoid 

 patches of black pigment. They possess four fully developed limbs, 

 and external gills, and are adequately fitted for an independent free 

 existence. They are very active and commence to feed at once. 

 Their normal diet consists of small Crustaceans, e.g. Daphnia, 

 Cyclops, and aquatic insect larvae, worms, &c. In captivity they 

 flourish well on the Enchytraeid worms sold by aquarist dealers if their 

 natural food is not available. They take these from forceps with 

 great avidity, and will also take small earthworms cut up, or small 

 shreds of meat, provided that the food offered is made to move. The 

 hyoid and four branchial arches are represented in the visceral skele- 

 ton, and they possess four gill-slits in addition to the external gills. 



4. Metamorphosis. 



They grow slowly and attain a length of ^^-^^ mm. in about i^-K^ 

 months, when they metamorphose and leave the water. The chief 

 external changes noticeable just prior to metamorphosis are the 

 appearance of yellow pigment, the approach to adult coloration, 

 and the dwindling of the external gills. The loss of the swimming 

 membrane on the tail follows immediately, and the head assumes the 

 adult shape through the advent of the paratoid glands. At the same 

 time profound internal changes have been going on. The cartilages 

 and muscles of the two most posterior branchial arches are normally 

 lost entirely, but the arteries and nerves remain. The tongue also 

 changes completely, the primary larval tongue being replaced by the 

 secondary adult structure (cf. p. 263), while the eye has had to become 

 adapted to see in air instead of in water. It is probably on account 

 of these considerable changes in the organs associated with gustation 

 and deglutition that the larvae show great reluctance to eat for a short 

 time just preceding and immediately following metamorphosis. Of 

 the internal factors which affect the inception and rate of metamor- 

 phosis the secretion of the thyroid glands takes the first place, while 



