152 THE AFRICAN BULL-FROG. 



burrows or crevices during the day, and only emerging from their refuge in the night-time, or 

 during rainy weather. Many species even dive below the muddy soil of pools as soon as the 

 water has nearly disappeared, and there remain moist, torpid, and content until the next rains 

 refill their home with the needful waters. 



Most of the Frogs have a power of changing the color of the skin, which is often found to 

 lose its brightest tints and become dark blown or nearly black in a very short space of time. 

 Any sudden alarm will often produce this change, the presence of a snake being an almost 

 unfailing means of effecting this object ; and it is known that the color of the Progs is greatly 

 affected by the locality in which they are at the time placed. The Tree-Frogs are more subject 

 to this change of color than the ordinary species ; but even the common Frog is well known to 

 alter from yellow to brownish-black in a very short space of time. Tins change is produced by 

 some mental emotion acting upon certain masses of pigment or coloring matter in the skin ; 

 and for a further elucidation of the subject, I must refer the reader to my "Common Objects 

 for the Microscope," where the pigment masses are drawn as seen through the microscope, and 

 their peculiar action explained. 



One of the most singular members of this group of animals is the Paradoxical Prog 

 (Pseud is pnradoxn ). 



This curious creature is a native of Surinam and South America, and is remarkable for the 

 enormous size of the larva, or tadpole. As a general rule, and indeed, as might be expected, 

 the generality of the batrachians are smaller in their larval than in their adult state ; the 

 tadpole of the common Frog being a good example. But the Paradoxical Frog exhibits a 

 phenomenon which is perhaps found in none of the higher animals, though common enough 

 among the non-vertebrated beings, and is less in its adult state than in its preliminary form of 

 tadpole. 



The tail of this tadpole is exceedingly voluminous, and the body has other envelopes 

 or appendages, which, when thrown off as it proceeds to its perfect state, reduce the bulk 

 so greatly that the earlier observers thought titat the creature reversed the usual order of 

 nature, and from a Frog became a tadpole. Some persons went (Men further, and said that it 

 was changed from a Frog into a fish. The appropriate title of Paradoxical was given to it in 

 allusion to this opinion. 



Strange, however, as this phenomenon may appear, and remarkable as it undoubtedly is, 

 it finds abundant parallels in the insects, where the larva is often of greater bulk than the per- 

 fect insect, or imago, as it is technically called. We may take for example the common silk- 

 worm, where the caterpillar is extremely large when compared with the moth into which it 

 afterwards changes; or that great, fat, bulky, subterranean grub which eats continually for 

 three years, becomes so obese that it is forced to lie .on its side, and afterwards turns into 

 the neat, compact, and active little cockchaffer. 



The color of the Paradoxical Frog is greenish, spotted with brown, and streaked irregu- 

 larly with brown along its legs and thighs. The snout is tapering and rather pointed in front. 



Our next example of the Pallida? is the African Bill-Frog. 



This line species is spread over the whole of Southern Africa, but is found most plenti- 

 fully towards the eastern coast, where it always frequents springs, pools, or the vicinity of 

 fresh water. It is most impatient of drought, and when a more than usually dry season 

 has parched the ground and rendered the hot soil uncomfortable for the delicate skin of 

 the creature's feet and abdomen, these Frogs are said to congregate in the pools in great 

 numbers, and just before the water has quite dried up. to burrow deeply into the soft mud and 

 there lie until the next rains bring the welcome moisture. 



Fifty of these large Frogs have been seen gathered together in one little pool, far from any 

 other water. It is, moreover, evident that they must have sonic place of couceatment, for they 

 are sure to appear in great numbers after a few heavy rains, and it is quite consistent with 

 probability that they should possess a simple and obvious method of preserving their lives 

 during the frequent droughts of the climate in which they reside. 



