532 Journal of the Asiatic Society of Bengal. [N.S., XVIII, 
do so are remarkable for their almost stony hardness and 
for the fact that they produce two kinds of gemmules or 
resting-buds, one kind capable of floating and being carried 
away by the stream, the other firmly fixed to the rocks. 
To turn from a small stream to a great river, something 
has also been done on the fauna of the Ganges. The only 
comprehensive paper yet published is Dr. Kemp’s account of 
that cf the Matlah River, which is now little more than a tidal 
creek running up the delta to the vicinity of Calcutta, but for- 
merly drained large salt lakes which have now disappeared. 
Dr. Kemp has shown that the animals, particularly the fish and 
crustacea, of the lower reaches of this creek have a remarkable 
resemblance to those of the deep sea. In most species this 
resemblance is superficial and clearly produced by convergent 
evolution, but one fish, the Bombay Duck (Harpodon nehereus), 
is closely related to deep-sea forms. The main resemblances 
between the fauna and that of the deep-sea lie in colour, dege- 
in both types of environment. 
The fauna of the Matlah River is, strictly speaking, marine 
or rather estuarine, but the presence of a marine element in the 
fauna of the Ganges itself far above tidal influence has long been 
known. I have discussed this element at length in a paper to 
be published shortly in the special volume of the Dutch Bij- 
dragen tot de Dierkunde ' to be issued in honour of the seventieth 
birthday of Prof. Max Weber of Amsterdam. The two most 
interesting regions in tropical river-systems are, from the faun- 
istic point of view, the mountain torrents and the deltaic efflu- 
ents. Jn both much still remains to be done in India. So far 
of the adhesive organs, etc. in a very thorough manner. In 
one paper, just issued in the Rec. Ind. Mus, Dr. Hora and 
I have discussed the “communal convergence” that exists 
between the larvae of so-called Ranae Formosae and the fish of 
the genus Garra or Discognathus and certain other genera found 
in mountain torrents. : 
of the papers cited in the bibliography the geo- 
graphical distribution of the species, genera or families concerned 
is discussed at length. The resemblance between the freshwater 
fauna of the Malabar zone and that of tropical Africa may now 
be regarded as well established, but it has been shown within 

! Now published in Bijdr. t.d. Dierk., Afi. 22 (1922). ° 

