Conchology. 1 67 



If no such glandular structure, or difference in the matter se- 

 creted, should be traced on the neck of the Helix nemoralis this 

 explanation of the cause of the variety of colors in shells would 

 appear extremely probable; but this probabihty amounts to cer- 

 tainty, from the actual observation of the existence of this pecu- 

 liarity of structure and effect. When the Helix nemoralis is de- 

 prived of part of its shell, the body appears of a vi^hite color, ex- 

 cepting towards the neck, where the white inclines to yellow, and 

 where besides there is a number of black or brown bands, equal 

 to that of the bands of the shell, and arranged in the same direc- 

 tion. It has been observed, too, that the individuals which have 

 only one black stripe on the shell, have only one single black spot 

 on the neck; and those having four spots on the neck, have four 

 stripes of the same color on the shell. These rays are placed im- 

 mediately under those of the shell; they commence at the dis- 

 tance of about a hne from the extremity of the neck, which is it- 

 self usually spotted with black all round. The existence, there- 

 fore, of these excretory organs can no longer be doubted. The 

 difference of color seems to prove the difference of structure. 

 But to establish this beyond the possibility of doubt, it is only ne- 

 cessary to have recourse to experiment, by observing what hap- 

 pens in the new piece of shell which is renewed, in place of that 

 portion which has been removed, and if it appear that the part of 

 the shell which is formed opposite to the black rays of the animal, 

 is black, and if that which is formed between the stripes, be of a 

 different color from that of the stripes themselves on the rest of 

 the body, no farther proof can be required. Now, it has been ob- 

 served, that the part of the new shell formed on the neck oppo- 

 site to the black or brown stripes on the animal's body, is itself 

 black or brown; that formed between the stripes is white or citron, 

 while the rest of the body is white, but different from that of the 

 neck, when it is of this color. 



It sometimes happens, that the part of the shell which has been 

 renewed is of a different color. This apparent deviation will ap- 

 pear less difficult to be reconciled to the explanation of the pro- 

 cess which has now been given, if we attend to the circumstance 

 that the new shell formed opposite to the neck of the animal is 

 never different from that of the old shell, excepting that the exter- 

 nal surface is extremely rough, and presents numerous furrows or 

 groovs, in place of the smoothness and fine pohsh of the old shell. 

 In this case, the inequality of surface is occasioned by the motion 

 of the animal retiring within its shell, before the new piece has 

 acquired sufficient consistency and sohdity; and thus the new 

 shell, having contracted on its surface wrinkles or furrows, the 



