814 MR EDWARD J. BLES ON THE 
can be seen passing back in a kind of helicoid vortex towards the cesophagus, where 
the two green currents converge and disappear. very day for ten weeks fresh 
culture must be added to the aquarium water; even so few as ten large tadpoles 
will clear twenty gallons of water in a single day of one added gallon of thick 
culture. When the water is clear they swim restlessly about like fish, as though 
searching for food, taking a gulp every now and then, as if to test the water, and 
then swimming on. As soon as fresh culture is poured in they immediately suspend 
themselves in mid-water and commence egulping regularly. That the current of 
water through the gill-slits is not kept up except when feeding confirms the state- 
ment made above that it is not a respiratory current. This method of feeding is 
so remarkable that it is desirable to find out whether it is normal in the natural 
habitat. It is interesting that the only Craniate known to feed in a similar way 
is Ammocetes ; according to A. SCHNEIDER its chief food is Huglena. In both cases 
the food is filtered out and then collected in a ciliary current. Xenopus tadpoles 
kept in Huglena culture were starved to death, however. Mr Brpparp’s tadpoles 
fed on Cyprids and nothing else; mine invariably rejected any small Crustacean 
which entered their mouths and starved amid an abundance of Ostracods and Cladocera. 
The movements of the tadpoles, their way of taking in water, the ciliated bands, 
the dorsal position of the mouth and the shape of the lips, all point to micro-plankton 
being a staple item of their diet, quite apart from the fact that they thrived on 
it. I would like to suggest that the swarms of Cyprids in the Zoological Gardens 
Tank were feeding on micro-organisms which also formed the staple food of the 
Xenopus tadpoles, the Cyprids being swallowed incidentally. 
The Mature Tadpole.—Fig. 24 is introduced to supply a more detailed figure than 
that published by W. K. Parker and copied in so many text-books. At the same 
time it should be observed that this tadpole in one important respect, which is probably 
diagnostic, differs from Parxesr’s. It will be seen that the long tentacles in fig. 24 are 
given off from the angles of the mouth; in fact a groove from the Junction of upper and 
lower lip is often continued up the base of the tentacle. Now, in all ParKer’s figures 
the tentacles are given off above the mouth, from behind the upper lip. The species to 
which Parker's specimens belong is, most probably, Xenopus calcaratus from Lagos. 
The attitude of the tadpole in fig. 24 is that taken when swimming rapidly in a 
vertical position to the surface of the water for air. The hind leg is stretched back, as 
in a swimming Urodele, and the resistance of the water as it shoots up seems to sway 
back the slender tentacles, usually directed straight forwards, into the position figured. 
There are three points in connection with this stage still to be mentioned, regarding 
the tentacles, the coloration, and the fore limb. 
Brpparp mentions that he “ more than once observed the tentacle of one side to be 
bifid.” This I found to be quite frequent among a limited number which reached this 
stage (length of 60 mm.); out of eight specimens, six had both tentacles branched. — 
Four of these, picked at random, are reproduced here. It will be seen that in A, B, and 
