70 ON THE HABITS OF XENOPUS L^VIS. [Feb. 4, 



Elizabeth ; and I have now the honour to lay before the Society the 

 results of my observations. 



Xenopus Icevis is called by the colonists the Plathanda. It is 

 commonly found in the Sunday, Zwartkop, Baakens, and Sharks 

 Elvers and the adjacent vleys. Its habits are essentially aquatic, the 

 animal never leaving the water except in search of places where food or 

 shelter are better supplied. Unlike other frogs, it feeds in the water, 

 on bisects, small fishes, or even young and larvae of its own kind, and 

 is apparently unable to feed out of that element. The mode of 

 eating is by forcing the prey into the mouth by means of the hands, 

 which act as a pair of claspers ; the deglutition always takes place 

 under water. Locomotion on land is by difficult and awkward 

 crawling and leaping. But Xenopus is a most admirable swimmer, 

 and remarkable for the manner in which it remains poised for a 

 long time immediately under the surface of the water, with the 

 nostrils only exposed. The whole structure of the animal denotes 

 its thoroughly aquatic habits — the broadly webbed toes, the smooth 

 slimy skin with its symmetrically disposed muciferous tubules; 

 there are no eyelids proper, but merely the transparent nictitating 

 membrane, moving up and down ; and the nostrils have a disk-like 

 internal valve. "When at rest, Xenopus never assumes a sitting 

 posture like other frogs and toads, and the back never appears 

 humped. 



Pairing takes place in early spring (August), when the male, 

 of which the palmar surface and inner side of the forearm acquire a 

 black horny layer, clasps the female with his arms round the waist, 

 the fingers interlocking on the pubic region. 



The ova are extruded singly and appear to be held for a short 

 time between the cloacal labial folds which are so much developed 

 in, and characteristic of, the female. I separated a pair during 

 copulation, and placed the female in a small clean aquarium, and 

 witnesyed the oviposition. After about 90 ova had been deposited, 

 I killed her for dissection and observed a small lot more of ova in 

 the oviduct. These did not hatch, thus proving that the cloacal 

 folds are not seminal receptacles. The eggs immediately after being 

 laid measured ^V '"ch in diameter ; 24 hours after, through swelling 

 of tiie mucilaginous envelope, they measured g inch. They are 

 found attached singly to aquatic plants or stones. After leaving 



them to be a type affined to the lowest Ecaudata, viz. the Discoglossidce and 

 Pelohatidee, though in many respects more specialized, i. e. diverging more from 

 the Urodele type. The larva of Xenopus, however, was known to approach 

 more nearly to the Urodele than to the Anui-ous type, as is exemplified by the 

 structure of tlje mouth without horny armature, by the two spiracula, and 

 especially by the presence of a pair of barbels which are the homologues of 

 the well-known 'balancers' of the Newt-larv£B. 



From Mr. Leslie's investigations we learn that Xejzo^ws agrees with the lower 

 Ecaudata {Discofflofsida, Pclobatidce, some Bufonids and Cyst ig7iaf hid m) in 

 being inguinamplex. to use the term proposed by de I'lsle, i. e. the male holding 

 the female round the waist during oviposition ; and with the Discoglossoid 

 genera Bhcoff/ossi'^ and Burnhiiintor, as well as with the Newts, in the mode in 

 ■which the eggs are deposited. — G. A. Boulekger.] 



