ANATOMY AND PHYSIOLOGY OF A SNAIL. IQ 



banded ; others are unicolorous and banded. Mr. J. W. Taylor, 

 in his "Valedictory Address as President to the Conchological 

 Society for the year 1887," published in The Journal of Conchology 

 for April, 1888, makes the following statement: "Nearly seven 

 years ago Mr. Ashford suggested to me the probability that 

 Helix cantiana, cartusiana^ etc., were once banded species, and 

 I am disposed to agree with his suggestion." But there seems 

 to me scarcely any foundation for such a supposition. In the 

 first place, the primary shell in the embryo of all species is 

 unicolorous ; in the second place, the youngest portion (nucleus) 

 of the secondary shell in all species is unicolorous ; in the third 

 place, unicolorous specimens are most common in aquatic forms, 

 where environmental circumstances have doubtless not been 

 so great as on land; in the fourth place, of a banded species 

 unicolorous specimens are invariably found ; and in the fifth place, 

 such a supposition is not general and comparative enough. Thus, 

 I am inclined to the opinion that all the species of our land and 

 fresh-water mollusca were once, and only, unicolorous. What 

 the causa causans of the future banding was, we are, practically at 

 any rate, in doubt. It remains as one of Nature's greatest arcana 

 for the great future to solve. 



In H. nemoralis and H. hortensis the bands vary in number and 

 degree of development, so that it is necessary to have some 

 system by which we can represent these variations on paper for 

 the use of our fellow-workers. The system is known by the 

 name of the system of the band-formulce. The type of each 

 species has five bands, which are represented by the figures 

 12345, the 123 referring to three bands above the periphery, and 

 the 45 to two bands below it. When a band is interrupted it is 

 shown by a colon, thus, 12:45 ; when slightly developed, by the 

 insertion of the figure representing that band below the line of 

 the others as 12345, when obsolete by a cypher, as 02345, or 

 ooooo ; and when two or more bands are fused together into one 

 band it is shown by bracketing the figures standing for the com- 

 ponent bands, thus, 123 (45), (123) (45). If more than five bands 

 be present the extra band is represented by the insertion of the 

 letter x into the formula, as 12 x 345 or i x 2345. 



