LIMITATION IN LOWER VERTEBRATES 143 



laid, and the formation of a nest or burrow to contain them. The 

 females alone perform this duty, and although in certain cases the 

 mothers exercise some guardianship over the young after birth or 

 hatching, the males take no interest in them. 



All the turtles and tortoises lay white eggs with a stout shell, 

 which may be thick and hard, or leathery. The females usually 

 make a hole in the ground, in some well-chosen locality, to which 

 they return year after year, and are at the pains to cover up the eggs 

 and so far as possible remove all trace of their presence — a necessary 

 precaution, as they are a favourite food of many different kinds of 

 animals. The female common European pond-tortoise selects a piece 

 of hard bare ground, which she moistens, and then bores a hole in 

 it with her tail, afterwards enlarging the cavity with her hind limbs 

 until it is several inches deep. The eggs are placed in this and then 

 the hole is filled up with earth and firmly stamped down so as to 

 leave no trace of the disturbance. The huge loggerhead turtle, 

 which lives in the warm seas of both hemispheres, comes ashore to 

 breed, and has been watched on the Florida coast. The female 

 scoops a hole in the sand, above tide mark, places the eggs in it, and, 

 having covered them over, returns to the sea and takes no further 

 notice of them. The young hatch out in six or eight weeks and at 

 once take to the water, selecting shallow rock pools. There is 

 great destruction of the young and of the eggs, and an unusually 

 large number of these is laid, sometimes as many as a thousand. 

 The green or edible turtle has similar habits, but is more careful 

 and lays as a maximum a hundred eggs. The females come from 

 great distances to well-chosen breeding-places on sheltered sandy 

 shores. They are shy and wary, looking for the presence of any 

 possible foes before they venture to land. Finally they proceed 

 just beyond tide-level, scoop out deep holes, lay the eggs, cover 

 them up and carefully smooth over the heap of sand that they have 

 dug out, to leave no traces of their operations, and are said to 

 return to the sea by a circuitous route, so that their nests cannot 

 be tracked out by the trail they leave on the beach. Box tortoises 

 lay a small number of eggs and secrete them in soft ground or under 

 leaves so carefully that the young have very seldom been found. 

 The female of the common Greek tortoise, which is often kept as a 

 pet, lays from two to four eggs rather late in summer, and buries 

 them carefully in the ground. Soon after the young emerge they 

 bury themselves, and do not reappear until next spring. The 

 South American " Arrau " turtle, the eggs of which are taken in 



