316 MARY H. HINCKLEY, NOTES 



stances might be cited, not only showing that the length of time varies according to the 

 temperature of early spring, but also that eggs laid at the same date may vary somewhat, 

 owing to some difference in the temperature of the water where they are laid. As the 

 season advances and the weather becomes warmer the eggs of all our frogs and toads de- 

 velop more rapidly; in the summer months I have found but a trifling difference in time. 



The tadpole escapes from the outer membranous shell with eyes and mouth in a rudi- 

 mentary state ; the external gills are often more advanced in development than is usual 

 with the other species of frogs and toads found here ; the nostril pits are conspicuous and 

 the holders, one each side below and back of the mouth, are prominent. The first stage 

 (Duges) is passed and the second entered on during the first week ; that is, the external gills 

 are developed and resorbed and the tadpole assumes the proportions it afterwards retains. 

 The gills on the right side disappear first ; with the resorption of those on the left side, 

 and junction of the thin membrane which has gradually grown downward to the trunk, the 

 branchial cavity and lateral spiraculum are formed. During the first week the mouth is de- 

 veloped so that the deep-brown, horny fringe of teeth at the edge of the lip and folds is 

 defined, and the eyes so that they have some sense of sight ; the latter are prominent, set 

 widely apart, and relatively large. The head and body are short and broad ; their united 

 length is contained about twice in that of the tail. As soon as the external gills are re- 

 sorbed the tadpoles leave the objects to which they cling by means of the holders, and may 

 be found darting in and out among the dead grasses and herbage along the shallow water. 

 By the tenth day the holders have disappeared. Like the tadpoles of Hyla versicolor, 

 which they so much resemble at this stage, they are extremely quick in movement and, 

 where there is space, do not herd together. Search for food (and for this they mouth 

 against whatever conies in their way, taking animal food eagerly, devouring one another 

 as soon as dead, or even while alive if too disabled to move), escape from enemies, with 

 periods for rest and sleep, appear to be the events of their existence during the larval 

 changes. As soon as the arms are thrown out the tadpoles are in haste to leave the water, 

 climbing the plants, sedge, or graceful panic and manna grasses (Panicum dichotomum, 

 Glyceria pallida) that often choke the shallow water ; the holding power of the dilated 

 tips of fingers and toes enabling them to cling to an object regardless of position. I have 

 found them a yard or more from the water before the tail was much resorbed, but for safety 

 they would immediately turn to that element. Tadpoles of Pickeringii ordinarily pass 

 about eight weeks in the larval condition. The same disastrous results that sometimes 

 overtake the larvae of sylvfdica and halecina are shared by Pickeringii in the evapora- 

 tion of the shallow water of swamps, bogs, meadows, and small ponds created by the spring 

 rains and melted snow and ice. They collect in the pools left where the water has receded, 

 shut in with water enemies, growing thin and maiufed, till the water here also evaporates 

 and all perish. It sometimes happens that the oldest tadpoles of sylvatica and Pick- 

 eringii are hurried through their transformation under these conditions before it is accom- 

 plished elsewhere, but both tadpoles and young frogs are pale in color and small in size ; 

 the former lacking almost wholly the metallic coloring usually conspicuously brilliant. All 

 trace of the tadpoles, left to perish, is soon gone. This wholesale destruction of life in one 

 direction is Nature's bounty in another. On the soft mud one finds a net-work of footprints 

 made by various birds, and now and then tracks of a skunk which, in his nightly foraging, 



