3+ R.. E. IvLOYD : Remarkable Cases uf Variation. [Vol. II, 



The following facts seem, therefore ^ to be well established : — 



(i) The great variabilit}^ of one feature (the raptatorial 

 claw) in a particular race of the genus Squilla. 



(2) The comparative stability of the same feature in other 



races of the genus from neighbouring seas. 



In reference to the same subject the following statements may 

 also be made, though the supporting evidence is much less sure : — 



(3) This variable race of the genus is very common in one 



localit}^ ; but is rare (or does not occur) outside that 

 locality. 



No exception can be taken to the first part of this state- 

 ment. The number of specimens actually taken at one hawl of 

 the net was recorded as over 500. It is not usual to obtain a new 

 species in such large numbers, though the records of deep-sea 

 dredging show similar results from time to time. 



The second part of the statement, that this variable race is 

 rare outside the particular locality where it was found, is, of course, 

 open to the objection that the fauna of Indian seas is ver}' imper- 

 fectly known. How far this is true of the genus Squilla is fully 

 shown in the above table, which shows the wide distribution of some 

 of the species on both sides of the Indian Peninsula. 



(4) This variable race occupies an environment (beneath 

 no fathoms of water, far from terrestrial influences) 

 which must be comparatively constant in any one 

 place, through considerable periods of time : fur- 

 thermore, the circumstances of this environment 

 cannot differ widely from those met with close to the 

 lOO-fathom line in neighbouring seas. 



This statement does not rest on any definite evidence, though 

 it appears generally true that the conditions of life beneath 100 

 fathoms of water must be less lialile to change than in very shallow 

 water or on land. 



The genus Squilla is usually found in shallow water. It is 

 comparatively rare in depths of over 50 fathoms. In the above list, 

 the depth has been noted in the case of specimens taken from other 

 than shallow water. It is not likely that increased depth of water 

 could in itself produce variation in the direction of an increase of 

 raptatorial spines. That it has no such influence is shown by 

 the species .S. stridulans, which has l)een taken from 68, 240 and 

 95 fathoms but shows only six raptatorial teeth, still more so by 

 the species S. tenuispina and 5. leptosquilla which have been taken 

 from 188, 95, 270 and 419 fathoms, for these species have only 

 four teeth. 



Theurctical considerations. 



Taking into consideration the nunil)er of teeth on the raptatorial 

 claw of all the known si)ecies of Squilla, it is difficult to l)elieve 



