28 FROGS. 



of 2 or 3 inches. Freshly laid masses are always of a very bluish 

 tinge. The eggs are usually found in shallow water, 6 inches to 2 

 or 3 feet deep, though occasionally eggs have been in water of a 

 gi-eater depth. The eggs of the wood frog are to be confused only 

 with those of the leopard frog. In the former, the egg mass is 

 globose (PI. jsJV, fig. 1) ; in the latter it is plinthUke. In the 

 leopard-frog egg, the middle envelope is evident to the naked eye, 

 which is not true of the wood-frog egg (fig. 1, G and H). The 

 eggs of the wood frog are free, and the outer envelope of each egg 

 keeps its spherical form more exactly than in the case of the leopard 

 frog, where the eggs are closer together and both they and the outer 

 envelopes smaller. The eggs of the wood frog are 3.6 to 5.5 mm. 

 from each other, while in the leopard frog the eggs are 2.6 to 3.6 

 mm. apart. The two egg masses can be separated easily in the 

 field by inverting the mass, thus reveahng the lower side of each 

 egg. In the eggs of the leopard frog the whiteness of the egg mass 

 becomes very apparent, but in those of the wood fro^ the general 

 effect is not decidedly that of whiteness, because of the evident 

 encroachment of the black of the upper half upon the lower side. 



The northern wood frog doubtless has breeding habits similar to 

 those of the eastern wood frog. 



The life history of the common toad will serve well enough as an 

 example of the life histories of our more conunon toads. At the spawn- 

 ing season hundreds of pairs may be recorded laymg at one time; 

 and in one instance 10 pairs were secured within an area Ih feet 

 square. Any water hole, ditch, or transient pool may contahi one 

 or more toads at this season. They seemingly prefer the shallower 

 waters and are apparently not particular whether it be grassy (PI. 

 VII, fig. 2), weedy, or swampy (PI. VII, fig. 1), or whether the bottom 

 be free or covered with fresh or dead vegetation. So lon^ as water is 

 at hand, their mam desideratum is met. In choice of a breeding 

 spot, then, the toad is easily suited and will use a greater variety of 

 localities than any other anuran. This species may begm s])awnmg 

 when the temperature of the air is 50 to 51°, but the crest of the 

 breeding season is reached at about 70°. Spawning may begin 

 when tlie water temperature is as low as 51° but reaches a maximum 

 when the water temperature is about 56 to 66°. The toad begins 

 ovulation about April 23, the earliest examples recorded being 

 April 5. The crest of ovulation comes a})out April 30. Thereafter 

 tlie number of spawnmg pairs diminishes. By May 15 or 20 the bulk 

 of tlie laying is about completed, and by May 20 or 25 nearly all the 

 toads' eggs are hatched. In June there are a few stragglers. In 

 rare instances the species lays through July. So, spaAvniiig in this 

 species occasionally extends far beyond the transformation time of 

 the first-liatched toad tadpoles of the season. Egg laying takes 

 place both by day and by night. The female toad lays from 4,000 

 to 7,000 eggs. The eggs are laid ordhiarily in quiet water; it may be 

 shallow, but not always so. The eggs are found m pools and ponds, 

 artificial or natural, in marshes, backwaters, ditches, etc. The 

 strings may rest merely on the bottom or be twined about vegetation 

 or sticks wliich ha])pen to be near at hand (PI. XVII, fig. 1). The 

 eggs are laid in long, spiral tu})es of jelly (PL XIX, fig. 2). Each 

 egg, with its quadrangular envelope, is incased in two tubes of joll^, 

 one tube within the other. (See fig. 1, A.) The hatchmg period is 



