FORMATION OF THE COCOON 619 



Reproduction of lost limbs. - - Here might be discussed the sub- 

 ject of the renovation or renewal of maimed or lost limbs, or Hit- 

 reparation of other injuries. As is well knoAvn, the coelenterates, 

 echinoderms, and worms under certain circumstances multiply by 

 self-division, or if artificially mutilated, the parts are gradually 

 restored by cell-proliferation or histogenesis. It is so with the 

 antenna? and legs of crustaceans as well as the digits and tail of 

 salamanders. The experiments first made by Le Pelletier 1 on spiders, 

 and later by Heineken, 2 and others after him, on different spiders, 

 as well as on Orthoptera and Hemiptera (Blatta, Reduvius, etc.), have 

 proved that antenna? and legs and other external parts which have 

 been injured or shortened, or entirely cut off in young individuals, 

 are replaced at the next, or after successive moults, though generally 

 in diminished size. This does not usually occur in adult life, and 

 the process of reparation of lost parts is apparently due to the 

 active growth of the cells of the parts affected during the process 

 of moulting, when the histolysis of the maimed or diseased parts 

 is succeeded by the rapid development of new cells, not only of the 

 hypodermis, but also of the more specialized tissues within. And 

 this tends to prove that such histolysis and making over of the 

 muscles and other structures within occur especially in all meta- 

 morphic insects, and also in ametabolous forms, though the process 

 has been most thoroughly examined in the Diptera, where these 

 changes are more marked. 



Gonin has found that the thoracic legs of the caterpillar corre- 

 spond only to the tarsi of the imago (Fig. 608). It results, he 

 says, from this fact that in accordance with the observations of 

 Reaumur (which were wrongly interpreted by Newport and Kiinckel 

 D'Herculais) that the amputation of the legs of the larva does not 

 involve the entire leg, but only the extremity of the leg of the imago. 



Formation of the cocoon. - - While the larvae of many insects, as those 

 of the butterflies, suspend themselves before transforming, and spin 

 no cocoon, or dig into the earth for protection and to secure an 

 immunity from too great changes of temperature, a large proportion 

 of the larvae of metabolous insects which lead an inactive pupal life, 

 line their earthen cells with silk, or spin a more or less elaborate 

 case of silk, called the cocoon. We have seen that the inactive pupa 

 of the male scale-insects is covered by the scale itself, or even in 

 one case the insect forms a true cocoon of fibres of wax. The aquatic 



1 Le Pelletior. A. M. L., Bulletin de la Societe Philomathique, Paris, April, 1813. 



2 Heineken, Carl. Observations on the reproduction of the members in spiders 

 and insects. (Zool. Jo urn., 1829, vi, pp. 422-432.) 



