MUSEUMS AND RESEARCH 75 



Now in mountain streams of the Malay Peninsula and 

 ArcMpelago there is a curious Cyprinid genvis—Gynnochilus — 

 which agrees with another genus from the same region — 

 Crossochilus — in most characters : form, fins, scaling etc. 

 But Gyrinochilus difiers from Crossochilus and from all other 

 fishes of the Carp family in several features connected with its 

 pecuUar habits ; it has taken to feeding on mud and has lost 

 its teeth, whilst the bones in the throat that usually bear 

 teeth are almost vestigial, and the horny pad they bite against 

 in other fishes of the Carp tribe has disappeared. Moreover, 

 as mud is not very nutritious, the fish has to extract the 

 nourishment from a large quantity at a time, and for this 

 purpose the intestine is very long — fourteen times as long as 

 the fish itself. Another peculiarity is that the hps surround 

 the mouth and form a fimnel-shaped sucker by means of which 

 the fish can hold on to stones in the torrents, and this is no 

 doubt useful also in gathering in the mud ; anyhow, whether 

 the fish is holding on to stones or has its mouth full of mud, 

 it cannot take in water for respiration through the mouth in 

 the usual manner ; this difficulty is overcome by having 

 the external opening of the gill-chamber divided in such a 

 way that the, water flows in through the upper part and out 

 through the lower. 



Now if — as some, experimental zoologists would have us 

 beUeve — evolution has proceeded by the sudden appearance of 

 new mutations and definitely inherited variations, some of 

 which will find an environment to which they are more or 

 less well fitted — if, in short, change of structure has preceded 

 change of function — we must regard Gyrinochilus as singularly 

 fortimate in that, although it has lost its teeth, it has managed 

 to do without them because it has acquired an intestine 

 sufficiently long to enable it to Kve on mud ; and its good 

 fortune has not ended there, for it has been able to use the 

 sucker which has been formed by the union and outgrowth of 

 its lips because, by a marvellous coincidence, it has evolved 

 an apparatus which permits it to breathe without taking in 

 water through the mouth. 



Gyrin.ochilus has not changed its form or its fins, but has 



