Mr. J. Higginbottom on the British Tritons. 373 



causes, the ovum becomes exposed to the water too early and 

 perishes. 



About a week after the ovum has been deposited, the embryo 

 acquires more of an oval shape ; in another week it increases in 

 size, and the head, body and caudal extremity are seen distinctly 

 through the transparent capsule which gradually increases in 

 size ; in about three weeks the embryo is perfect and beautifully 

 formed, and moves quickly round within its envelope, which is 

 now much distended. 



About this period the tadpole escapes from the capsule, when 

 in water freely exposed to the open air, but its development is 

 modified by circumstances, such as situation, temperature, &c. 



I kept some ova in a room with a south aspect at 60^ Fahr., 

 and the tadpoles escaped in fourteen days. I placed other ova, 

 which were deposited on blades of grass, in a deep, dark, rock 

 cellar, at 48° Fahr. ; they were fully developed in these in three 

 weeks, the same time as some others placed in the open air at 

 55° Fahr. ; but after quitting the ova, the growth of those tad- 

 poles in the cellar was materially impeded ; the facts of which 

 are given in my paper "On the Influence of Physical Agents on 

 the development of the Triton and Frog,'' published in the Phi- 

 losophical Transactions, Part 2, for 1850, p. 431. 



III. The Development of the Tadpole and the young Animal. 



At length the ovum bursts, and the tadpole escapes and swims 

 freely away ; it rests or suspends itself on the edge of a leaf, or 

 on a blade of grass, or on the oblique sides of the vessel. It 

 sometimes remains on the bottom of the vessel, lying on one side, 

 as if inanimate or unable to sustain itself, but on being disturbed 

 it quickly swims away. 



Shortly after the tadpole quits the ovum it feeds voraciously 

 on aquatic larvae, animalculse and small animals in the water. 

 I have seen the Triton asper in its branchial state with three of 

 the smaller species in its stomach at one time. The Triton re- 

 mains in the water in the tadpole or fish -like state until its 

 branchiae disappear and its legs become sufficiently strong to 

 enable it to quit this element. The development and growth 

 of the legs is very tardy; the anterior extremities are about 

 twenty-one days in being formed after quitting the ovum ; the 

 posterior about ninety days, and they are then extremely fine 

 and delicate; but as the legs become stronger, the branchiae 

 gradually disappear and the opercula close over the gills. When 

 these changes are accomplished, the animal leaves the water and 

 becomes entirely terrestrial. This occurs generally in September, 

 between the first and last week in that month ; but to this rule 

 there is an exception, which I first observed in October 1845, 

 on exan-ining some pools where Tritons of both species abound 



