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90 ANNUAL REGISTER For the YEAR 1772. 91

draw their heads, so that only the skin, with a small part of the head, was in reality cut off.  He repeated these experiments again the succeeding year, but with no better success than before; and I have myself tried the same without the least appearance of any reproduction which has suggested to me the following reflections: Out of thousands of snails who have suffered the operation by different observers, there have not been above five or six of them which have, as it is pretended, reproduced their heads; this affords a suspicion, that there may be some mistake in regard to these few, on whom the operation is thought to have succeeded; and that the great number of those which died, was owing to the operation having been but too surely performed; whilst, on the other hand, the small number of those which survived, and reproduced (as was supposed) their heads, owed their lives to the defect of the instrument used for the operation, whereby they had time to contract and withdraw their heads to avoid the fatal stroke.  This is confirmed by another circumstance observed in those snails, which are pretended to have recovered their heads, namely that their horns (as they are called) were found to be shorter and thicker than before: this was probably caused by their having lost only a part of their head and horns; the remainder of their horns would naturally grow thicker by the conflux of humours at the wounded extremity, as is observable in regard to trees and animal in the like cases.  But it will be asked, why then are not these amputated horns perceived immediately after the operation, and not until a considerable time afterwards, when there begins to be a sensible expansion of the parts, as if there was some progress made toward the reproduction of the head?  I answer, I am persuaded that in all cases, where a reproduction of the head is pretended, the snail in reality never lost it, but only suffered an amputation of some of the skin and outward parts of it; and the wound occasioned hereby would require some time, before nature could repair the damage done, as in the case of all wounds: the snail therefore might for some time after the operation, issue from its shell without pushing out its amputated horns, on account of the pain and swelling occasioned by the wound; and of this I have been often a witness, when no part of their horns have been really cut off, but only wounded, they have crept out of their shells for several days, without putting out their horns, so that one would have thought them entirely cut off.  At last the horns have appeared, when they were recovered, and hence without doubt in many experiments they have been erroneously thought to be reproduced.  The same perhaps has been the real truth in those cases, where the whole head has been thought to be reproduced; in fact only some part of it has been cut off, or wounded, not fatally; and at last when the wounds have been healed, on its being pushed out again, it has been supposed to be reproduced.  So far have I been from finding any head reproduced, that I have not been able to procure a reproduction of any part of the horns which were really cut off, nor yet of any of the outworks (as I may call them) of the head. However, thus much I have proved, that snails will live a considerable time after their heads are cut off. Mr. Wartel preserved one without a head form October until the next May. I have myself kept one during a whole year; and consequently, during all that time it received no nourishment. But this length of its life, after such an operation, depends greatly on the time of year when the operation is performed. If the head be cut off in the Spring, it will soon die; because then if stands most in need of nourishment, after having been five or six months without any. But if the operation be performed in the autumn, it may live all the winter, and possibly all the spring, in case it be kept in a place not exposed to much heat. Nevertheless this preservation of them for so long a time, depends much on the manner of cutting off the heads: when I have performed the operation with a pair or scissars, which is the most effectual way, some have died in eight days, and others in a few month; only one lived a whole year, and gave me some hopes of a reproduction, but at last died also. These circumstances again give a strong presumption, that, when the operation is performed with a knife, the snail finds means to withdraw its head time enough to save some of the most important part of it. Nay, even when I performed the operation with scissars, I have observed their agility in preserving their head; so that often when I have thought that I had their heads and horns on my scissars, I have seen them soon after creep out of their shells with both head and horns, it being only the outside skin of  both which I had stripped off with my scissars. The same case has doubtless happened to others, who, after a time, have supposed a reproduction of both head and horns. The snails thus mutilated only have generally died. If any one should think, that some different curcumstances of either seasons, climates, ages, or species of snails, or other differences, may be a cause why a reproduction has succeeded with some and not with others; I reply, that I have neither made myself, or have been witness to experiments made by others, under every variation of circumstances, and have never yet been lucky enough to meet with a reproduction. That the snails in Italy, on which M. Spalanzani made his experiments, should be so different from those of France in this property alone, one cannot easily comprehend. When M. du Verney shall publish his observation read before the Academy of Sciences, we shall doubtless find his subject set in a clearer light. 
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Some Account of the Aquatic Spider; from a French work lately published. 
this species is found but seldom in Champagne among the lakes and marshes; it is in some sort amphibious; for it can live on earth as well as in water, and comes often to land for its food; yet it swims well in water, both on its belly and back: it is distinguishable by its brightness. In the water its belly appears covered with a silver varnish, which is only a bubble of air attached to its belly by means of the oily humours, which

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