208 FAUNA OF SHROPSHIRE. 



pairs each female accompanied by a male and that the 

 latter is in most cases smaller than his mate. In all Amphibia 

 the eggs are enclosed in a gelatinous sheath which, as soon 

 as they are laid, rapidly absorbs water and swells up till it 

 forms a thick transparent layer, through which the small 

 dark spherical yolk can be plainly seen. The form 

 of this gelatinous envelope varies with the genus. In the 

 Toad (Bufo), it is long and rope-like, the eggs being disposed 

 in a zig-zag manner throughout its length, and the whole hangs 

 in festoons from the water- weeds. In the Frog (Rano), each 

 egg is in a separate globular sheath, but the whole mass of eggs 

 adheres together in an irregular heap. In the Newt (Molge), 

 each egg is deposited separately and wrapped by the parent 

 in a leaf of a water-plant, held in a coil around it by the 

 glutinous nature of the envelope. Very rarely, the writer 

 has known the Newt to deposit its eggs on the clay at the 

 edge of a pond and spread the clay over them, but this was 

 because there were no suitable weeds in the pond. The yolk 

 in the eggs that are laid in the early spring is black, but in 

 those deposited later on in the year it is of a lighter colour. 

 It has been surmised that this difference is due to the fact 

 that the early eggs need all the warmth they can collect, and 

 black absorbs more heat-rays than any other colour. There 

 is also a difference in the buoyancy of the spawn at the two 

 periods that laid in the cold season is heavy and remains on 

 the ground below the water, where it is beyond the reach of 

 night-frosts ; later on the spawn floats. Temperature and 

 sunshine are important factors in the development of the 

 spawn, as also in the rate of growth of the tadpoles after 

 hatching, and if either eggs or tadpoles are kept cold and in 

 a dark place, they may be retarded almost indefinitely. 

 Under favourable conditions the eggs hatch in about twenty- 



