ARACHNIDA. 



215 



domen, but the spider soon entirely frees itself 

 from it. This is the mode in which the young 

 spiders of every species disembarrass themselves 

 of the egg-covering, and the operation is analo- 

 gous to that of moulting. This is, however, 

 only the first birth : all the parts of the spider, 

 the head, the jaws, the legs, the abdomen, are 

 still enveloped by a membrane which furnishes 

 to each a sort of sheath. The spider is embar- 

 rassed in all its movements; it changes its 

 situation with apparent pain, and is unable to 

 construct a web and seize its prey : it seems in- 

 deed to be stupified and indisposed to action. 

 To this end, and in order to be fit for locomo- 

 tion, it is necessary that it should free itself of 

 this other covering ; and it is only then that it can 

 be said to see the light. This last operation, 

 or as it may be termed the first rnoult, takes 

 place after a period, varying according to the de- 

 grees of atmospheric heat and moisture. Some- 

 times it is observed within the first week, at 

 others it is not effected before the end of several 

 weeks. In every instance the moult takes 

 place in the woolly nest or general envelope of 

 all the eggs, and the young spider does not 

 quit this common nest, except in fine weather, 

 generally in the months of May and June. 



Before arriving at the adult state the spider 

 changes its skin many times, and even after that 

 period it is still subject to moults, which occur 

 every year in the spring, and after the exclusion 

 of the eggs. Up to the present time it has 

 been admitted that the Arachnidans, from the 

 moment of their exclusion to their adult state, 

 undergo no metamorphosis, but are subject 

 only to the moultings of which we have just 

 spoken. This circumstance has even been em- 

 ployed by zoologists as a character distinguish- 

 ing the arachnidans from the class of insects, 

 which generally undergo metamorphoses in pas- 

 sing through the conditions of the larva and 

 chrysalis. The observation holds good for the 

 greater part of the Arachnidans, but there are 

 many of this class, which, in passing to their 

 adult condition, undergo changes which cannot 

 but be compared with the metamorphoses of 

 insects. Such, for example, are many of the 

 acaridtf, upon which M. Duges has recently 

 fixed the attention of naturalists.* 



We cannot conclude the present article, 

 without briefly noticing a very curious phy- 

 siological phenomenon which has been ob- 

 served in the Arachnidans, and which has 

 long been noticed in the class Crustacea : 

 we allude to the faculty which these animals 

 possess of reproducing their limbs when these 

 have been accidentally lost. This property, 

 which belongs to the spiders, (aranete,) was 

 generally doubted, until a distinguished natu- 

 ralist, M. Lepelletier, published the result of 

 his experiments ; the fact is of too much im- 

 portance in science not to be dwelt upon with 

 some detail. Spiders which have lost a limb, 

 according to this observer,! are always found 



See his interesting Memoir in the Annales des 

 Sciences, Nouv. Serie, torn i. and ii., 1834. 



t See Bulletin de la Societe Philomathique, 

 Paris, Avril, 1813. 



to have lost it entirely, that is, the femur, tibia, 

 and tarsus, are all wanting. A portion of a leg is 

 never found detached at one of its joints.nor bro- 

 ken off between two joints, nor the femur remain- 

 ing adherent to the body by itself, or with the tibia, 

 the rest of the leg being lost. If by accident a 

 spider should be met with in any of these con- 

 ditions, it is either dying or dead. But M. 

 Lepelletier remarks that those which have lost 

 one or more entire legs, are not less lively on 

 that account. 



To explain these circumstances our author 

 commenced a series of experiments on spiders, 

 in the year 1792, with the following results: 



The smallest wound in the thorax or abdo- 

 men of a spider is mortal, and that in a very 

 short time, on account of the loss of the internal 

 nutrient fluid, which cannot be staunched. 



If a 'leg of a spider be cut off with a sharp 

 instrument either at one of its joints, or in the 

 interval of two, leaving a part of the limb ad- 

 hering to the body, the spider appears to suffer 

 considerably ; it endeavours to tear off the rest 

 of the leg ; if it succeeds, it again acquires its 

 powers of moving, and the hemorrhage soon 

 ceases ; in the contrary case it perishes in 

 twenty-four hours. 



The luxation of one of the joints, or the frac- 

 ture of the femur or tibia in the middle are 

 equally mortal, if the spider does not soon dis- 

 embarrass itself of the leg which has received 

 the injury. 



It is necessary here to make a remark upon 

 the anatomy of the legs of spiders and crusta- 

 ceans ; they have the first joint short, which 

 connects the leg to the thorax ; M . Lepelletier 

 calls this the haunch, coxa. If a spider be 

 seized by the extremity of one of its legs, and 

 is left at liberty to make its efforts to escape, 

 the leg will be separated from the body at the 

 junction of the femur with the coxa; and the 

 same thing takes place when the body of the 

 spider is held fast, and the leg is pulled off. In 

 both these cases the spider seems not to suffer 

 pain ; it experiences only a very little loss of the 

 internal fluid, and does not die in consequence ; 

 it spins, seizes its prey, and oviposits in the or- 

 dinary manner. 



The preceding facts are applicable to all 

 spiders, (aranea,) and M. Lepelletier has ob- 

 served them repeatedly in many of the common 

 species. The following experiments have been 

 made only on the domestic spider, (Tegenaria 

 domestica, Walck.) because it can be preserved 

 in a lively condition, and for many years in a 

 glass vessel. 



We have successively observed a great num- 

 ber of individuals of this species which were 

 mutilated of one or more legs. It was not 

 without surprize that the author of this article 

 observed the first spider that was experimented 

 upon, and which wanted a leg, change its skin, 

 and after that operation reappear with eight 

 legs. The like occurrence was frequently ob- 

 served ; the new leg was two or three lines in 

 length when it first appeared, that of the oppo- 

 site side being less than an inch : each of the 

 joints of the former continued to grow during 

 the whole of the year. 



