TADPOLES OF XENOPUS 



life in the pond wave. Their hind feet are most obtru- 

 sively webbed, and along the sides of the body are a 

 row of what look like rather careless stitches ; the baggy 

 and ill-fitting appearance of the frog suggests an amateur 

 attempt at repair. These stitches are in reality the 

 organs of the lateral line, a structure found in the lower 

 amphibia and in fishes, a sense organ probably of 

 the nature of touch. The absent tongue is also ap- 

 parently to be looked upon as the result of an aquatic 

 life, where food slips into the mouth and is not 

 manoeuvred thereto by the prehensile organ of the 

 buccal cavity. The lungs are assisted in their contrac- 

 tions by a very complicated system of muscles, as are 

 those of Pipa. This is exactly analogous to the in- 

 creased diaphragm in whales and in other aquatic 

 mammals, and is a very remarkable instance of how 

 Nature attains to the same result without the manu- 

 facture of a special organ. A new one is simply made 

 use of, and, if need be, increased and altered. An im- 

 perfect representative of the Xenopine and Pipine 

 " diaphragm " exists in Rana. There is nothing pecu- 

 liar in the breeding habits of Xenopus, such as occurs in 

 its ally Pipa. It lays eggs in the ordinary amphibian 

 way, and therefrom emerge tadpoles. These tadpoles 

 are quite as interesting in their way as are their parents. 

 Some few years back there were swarms of them at the 

 Zoo, a pair of the frogs recently brought back from 

 Zanzibar having laid eggs. They have not bred since, 

 but there is always the chance of their doing so. The 

 home-bred tadpole is familiar enough to everyone by 

 its imp-like aspect and alluring wrigglings. The tadpole 

 of Xenopus is about as different as it can be and yet 

 remain a tadpole. It is clear and glassy in colour, with 

 only a faint amount of pigment here and there ; and it 

 has a fascinating way of standing upon its head at the 

 bottom of the tank and wriggling its tail violently. 



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