THE FROG (Rana) 



THE PLATANA ok CLAWED TOAD (Xenopus) 



External Features. 



First Day 



1. Make a drawing of the dorsal surface of the Frog (or the Toad), showing : 



(a) The nostiils or external nares. 



(6) The eyes, each with two eyelids. The upper eyelid is weU developed, 

 pigmented, and almost immovable ; the lower one is a mere fold of 

 skin, produced into a thin, transparent and freely movable nictitating 

 membrane. [In the Platana there is also a short tentacle beneath the 

 eye.] 



(c) The circular tympanic membrane, situated just behind the eye. [This is 



absent in the Platana.] 



(d) The opening of the cloaca, on the dorsal surface and between the legs. 



[In the female Platana there are three conspicuous folds of skin arownd 

 the cloaca.] 



(e) The limbs and their divisions. 



[(/) In the Platana the skin has tube-like lines rownd the body. These are the 

 openings of the slime glands, with which the skin is richly supplied.] 



Fig. 64— a. The Frog [Rana), nat. size ; B. The Platana or Clawed Toad (Xenopus), reduced. 



2. Make an enlarged drawing, about twice the natural size, showing : 

 (a) The fore-limb, consisting of upper arm, fore-arm, and hand with four 

 complete digits (the first digit, the poUex or thumb, being an incon- 

 spicuous rudiment), 



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