ON THE HABITAT AND FOOD OF HELIX 

 DESERTORUM. 



Ry the Rev. A. 11. COOKE, M.A., 

 Head Master of Aluenham School. 



Two recent visits to Egypt, in the winter of 1903 and 1904, enabled 

 me to examine carefully the conditions under which this species lives, and 

 which suggested certain interesting problems 



Helix deserforiiin is abundant in the neighbourhood of the Pyramids of 

 Ghizeh. It does not appear to inhabit the cultivated district at all. The 

 ground on which the Pyramids stand is sheer desert, loose sand, stones, and 

 bare rock. At first sighr, not a single living plant appears, but careful 

 search will reveal, here and there, a few dry stubly wisps. Near to them, a 

 few desertorum may be found, but the great mass of living specimens are at 

 least 500 or 600 yards away, on a plateau which appears utterly destitute of 

 vegetable life. Here the species abounds ; the young live gregarious under 

 stones, which shield them from the burning rays of the sun, while the adults 

 Occur, for the most part, singly in the open, some attached to rock, the 

 majority scattered about on the open face of the smooth sand. I may 

 remark parenthetically that, at the time of my visits, which were in the 

 months when rain occasionally falls, the food conditions were presumably at 

 their optimum, and not an atom of food was to be seen. There was no 

 appearance of " aestivation " or " hibernation" : the adults were as fat as 

 butter, and evidently \n prime condition. 



The problem naturally suggested itself, ^^' hat do the creatures feed on ? 

 Cannibalistic tendencies are out of the question, for the radula is of the 

 normal type represented by H. asjjersa. It occured to me that an examina- 

 tion of the excreta might supply some answer to the question, and accordingly 

 I collected a number of specimens, carefully brushing away all traces of 

 sand from the region of the mouth, and, on returning home, handed a 

 selection from their excreta to my senior science-master, Mr. J. M. Wad- 

 more, M.A., F.C.S., for analysis. He reports as follows : — 



" I have much pleasure in giving you the result of my examination of 

 the Egyptian snails' excreta. 



"Broadly speaking, the material consisted of two portions, (i) Sand, 

 forming about half the total weight ; (2) a fluffy, fibrous substance. The 

 latter was extracted with warm dilute hydrochloric acid, in which a small 

 portion dissolved, but the greater part remained unaffected. 



" The solution thus obtained was coloured with organic matter, the 

 nature of which I was unable to ascertain. I succeeded, however, in estab- 

 lishing the presence of iron and calcium, both in relatively considerable 

 quantity. Potassium I was unable to detect, even by means of the spectro- 

 scope, and though I should not like to say defmitely that this metal is 

 absent, I feel sure, at any rate, that the amount must be excessively small. 



" In the portion undissolved by the acid, I found unmistakable indica- 



