178 Memoirs of the Indian Museum. [Vol.. II, 



British Museum, Oxford University Museum, Cambridge University Museum, United 

 States National Museum and the Aberdeen University Museum. 



Before considering the theoretical aspects of the case the following facts must be 

 emphasised : — 



1. The '^Investigator" has trawled 380 times in the deep waters of the Arabian 

 Sea and the Bay of Bengal. Twenty-one of these Stations were in water between 

 100 and 500 fathoms, in the neighbourhood of the Andaman Isles, — that is to say, in 

 situations where we should expect to obtain Malthopsis. 



2. Only four of the twenty-one Stations have yielded Malthopsis. Some of the 

 localities are separated by considerable distances though all are in the neighbourhood 

 of the Andamans. The position of the Stations is given on the map (text-fig. 8). 



3. The smallest number of specimens obtained at one Station is four (commu- 

 nity C) ; the largest number is ten (community A). The genus is therefore not rare 

 at the Stations at which it was obtained, but it is not generally common in the 

 moderate depths of the Andaman Sea, for not a single specimen was obtained at the 

 seventeen other Stations, nor has it ever been obtained elsewhere by the " Inves- 

 tigator." 



4. The physical conditions under which the four communities live must be 

 remarkably similar. 



5. The genus Malthopsis is not confined to Indian seas. A number of species 

 have been described by Garman from the Pacific Ocean. These, however, must 

 represent a separate branch of the genus, for they do not possess the characteristic 

 nasal spine. The species Malthopsis mitrigar (Gilbert and Cramer) from near the 

 Hawaiian Isles po.ssesses this spine. It would be most interesting to know how it 

 resembles or differs from any of the five types described here as regards the arrange- 

 ment of its ossicles. 



Theoretic AI. considerations. 



It is fortunate that this case can be illustrated by photography so that it lies 

 open to the consideration of all, for such wide and definite variation as these com- 

 munities exhibit is rarely met with. 



In regard to the change which may take place in organisms, it has been written 

 '' There are two factors: namely, the nature of the organism, and the nature of the 

 conditions. The former seems to be much the more important ; for nearly similar 

 variations sometimes arise under, as far as we can judge, dissimilar conditions; and, 

 on the other hand, dissimilar variations arise under conditions which appear to be 

 nearly uniform " {Origin of Species, page 6, 6th Ed.). There are two reasons given 

 here for the statement that the nature of the organism is much the more important 

 factor in producing change. The present case forcibly illustrates both reasons. At 

 any one of the four localities where, presumably, the conditions are uniform, different 

 varieties seem to have arisen, and at any two localities where, presumably, the condi- 

 tions might differ, similar varieties have arisen. 



Therefore, as regards Malthopsis it may be said that the nature of the organism 

 is much the more important if not the only factor in the change that is occurring. 



