254 CEKION, GROUP XI. 







MAYN., t. c., p. 173, f. 57. S. resiricta MAYN., t. e., p. 175, f. 58. 

 S. crassicostata MAYNARD, unpublished. 



Cerion cinereum Mayn., BALL, Bull. Mus. Coni|). Zool., xxv, no. 

 9, p. 119 (Nassau, Gun Cay, Great Ragged Cay) ? C. glans 

 Kiister, Dall, t. c., p. 117 (Watling Island) C. glans Kiist., 

 PILSBRY, Nautilus, xii, p. 26 (Gun Cay) ? Cerion neylectum 

 Mayn., DALL, t. c., p. 120 (Great Stirrup Cay). 



This is a widely distributed species extending from New Provi- 

 dence and Andros westward to islets on the western edge of the 

 Great Bahama Bank. South of New Providence it has been modi- 

 fied into larger forms which may be allowed specific rank. 



As usual in Cerion, every " colony " has its own characteristics of 

 coloring and form, and its own cycle of variations. In the mass or 

 average of specimens from a single spot, these local peculiarities are 

 often quite perceptible, sometimes striking ; but the variations among 

 individuals of any colony fully cover the differences between col- 

 onies, so that if we conventionally represent the single colony by a 

 circle, the periphery of which stands for the extremes of variation, 

 then the series of colonies could be represented by a series of such 

 circles overlapping in Tarious degrees, sometimes forming chains, 

 sometimes complexly interlaced groups. Where one has a large 

 series from any one point, it is easy to see that the variations within 

 a single " family " are frequently greater than the differences be- 

 tween several such colonies. 



It is this complete intergradation between colonies, even if shown 

 by but a small percentage of individuals, which causes me to reject 

 as species the forms defined by Mr. Maynard. That these local 

 forms. exist, distinguishable in the majority or average of specimens, 

 has been established by Maynard, beyond controversy ; but they are 

 not " species." They are " physiological varieties," which owe 

 their characteristics to the immediate action of the environment, and 

 respond to any changes therein. There is every reason to believe 

 that some of Mr. Maynard's " species " may be produced in one 

 generation by changing the food plant from a woody shrub growing 

 in a sterile place, to succulent herbage in a more favorable soil, just 

 as a plant growing on a hard roadside will be stunted, bear few and 

 comparatively simple leaves and a single flower, perhaps, while in 

 the cultivated field hard by it will attain greater size, different 

 shaped leaves, profuse inflorescence, etc. That C. glans varies con- 



