58 



HARD IV I CKE'S S CIE NCE-GOS SIP. 



THE NATURAL HISTORY OF THE TOAD. 

 By J. Arthur Eisdel. 



THE toads [Bufonidcc) are a family of the sub- 

 order sabentia, order batrachia, class amphibia, 

 division vertebrata. Only two species are British, 

 viz., Bufo vitlgaris, the common toad, and Bnfo 

 calamita, the natterjack toad. 



I shall confine my remarks to one member of this 

 family, Bufo vulgaris, the common toad, beginning at 

 the earliest visible stage of his existence, namely the 

 egg, tracing that existence on to maturity, and then, 

 having thoroughly gone into the toad's natural history, 

 I shall examine a general question or two about him ; 

 after which I will just describe the natterjack toad, 

 Bufo calamita. 



In the months of March and April may be found 

 in great abundance in the stagnant water of many of 

 our ditches and ponds the ova eggs or spawn of the 

 toad. These ova are arranged in a double series, 

 placed alternately and perfectly regular, and are 

 enveloped in a jelly-like mass which forms a con- 

 tinuous line, extending to the length of three or four 

 feet, sometimes even twenty or thirty feet. 



The embryo (for whose development immersion in 

 water is necessary) is found, in the first place, to 

 consist of a small globular body. In a short time the 

 sphere begins to elongate, the head becomes pro- 

 minent, the tail begins to show itself. In time also 

 a small projection takes place on each side of the 

 head, which is the earliest indication of the branchia' 

 or gills, which soon become visible and gradually 

 more developed. In a short time longer the first 

 voluntary motion of the embryo is discovered on the 

 application of any means of disturbance, but it con- 

 sists only of a slight movement of the head or tail. 

 Later on there is a slight division of the branchiae 

 into lobes, and the appearance of the beautiful phe- 

 nomenon, the circulation of the blood through these 

 organs. 'Hie embryo, which is still confined to a 

 curved position by the envelopes, now frequently 

 extends itself by sudden jerks as if to get free, which 

 it eventually does by tearing the membrane of the 



egg- 



The tadpole, as the little creature is now called, is 

 now hatched. In our own climate, in the ordinary 

 temperature of our spring, this hatching does not 

 take place until at least a month. The development 

 may be greatly hastened by a constant elevation of 

 temperature. After hatching, the branchiae speedily 

 enlarge, and continue to do so till they arrive at their 

 maximum of development. No sooner do these 

 branchiae arrive at this stage than they begin to 

 diminish in size ; they become obtuse and arc- 

 gradually so reduced as to be withdrawn within 

 the branchial cavity, and concealed by a little oper- 

 culum of the integument. When this is done the 

 tadpole has the form of an enormous belly and head 



in one undistinguishable outline. The eyes are now 

 perfectly formed ; the holders, which are small simple 

 organs placed on the under surface of the head, 

 enable the little animal to attach itself by means of 

 a viscid secretion at their extremities, have become 

 much diminished in size ; the mouth, which has 

 horny cutting processes, has acquired movable lips, 

 and the little creature, which has hitherto derived its 

 sustenance from its own resources, or by absorption, 

 now seeks its food amid softening and decomposing 

 vegetable matter, which forms its principal nourish- 

 ment until it reaches the toad stage. The tadpole 

 now undergoes but little change in its external form 

 for a considerable time, but increases rapidly in bulk. 

 On examining the tadpole internally we find that it 

 has an extremely long intestinal canal coiled spirally 

 within its large abdomen, which, for a reason I will 

 mention later on, is very long in proportion to the 

 length of the tadpole's body. Now how does the 

 tadpole breathe ? The water enters the mouth by 

 the orifice of the nostrils, which are supplied with 

 valves. When in the cavity of the mouth, which is 

 well closed on all sides, with the exception of the 

 throat, where are placed the branchial slits, the 

 water acted upon by the muscles, which cover them, 

 traverses these spaces and bathes the branchiae before 

 its exit through the branchial holes. The blood 

 which is driven by the heart into the branchial 

 vessels is then distributed, as it is in the fishes, in 

 fact the respiration and the circulation of the tadpole 

 are very similar to those processes in the fishes. And 

 now return to the exterior of the tadpole. By-and- 

 by a little tubercle appears on each side of the vent ; 

 this tubercle soon acquires somewhat the form of the 

 perfect limb, the toes budding as it were at the 

 extremity, but still it continues very short. Mean- 

 while the anterior extremities are also budding forth 

 in the same maimer and gradually assume their 

 distinct and final form, though not so soon as do the 

 hind limbs. As the_ hind limbs become developed, 

 the tail, the former organ of progression, is removed 

 by absorption, not thrown off as has been erroneously 

 stated. This is a gradual process, the absorption 

 beginning at the apex and progressing onwards to 

 the base until the whole is removed, so that the 

 posterior part of the body becomes rounded. The 

 tadpole's mouth too widens, and the eyes are guarded 

 by eyelids, while the belly lengthens. Externally the 

 tadpole has now assumed the form of a young toad ; 

 let us see what has been going on internally. The 

 intestines have become shorter, the branchiae have 

 been removed by absorption, and most beautiful 

 cellular lungs have been developed, while the circula- 

 tion has undergone an entire change. I may add 

 that it is not until the approach of autumn that the 

 young toads, having assumed that form in manner 

 just described, come to seek their food on the land. 

 And now we will suppose our young toad to be full 

 grown ; let us examine it. Its skin_ is naked, as it 



