in Course of Regeneration in Arthropoda. 315 



as the mutilated antennte of the same crustacean ctow in a 

 spiral until the first moult after the injury. 



The difference between the two modes of growth is not so 

 great as at first might be imagined. Let us see in what it 

 consists. In Arthropods showing spiral growth, as in those 

 which present the rectilinear method, the surface along which 

 the separation is made between two successive joints of a 

 limb becomes covered by a thin non-chitinous cuticle. In 

 one case as in the other the work of regeneration begins not 

 over the whole surface of the cut, but near the central part, 

 and growth is generally much more rapid in length than in 

 diameter, with the result that the rudiment of the limb in 

 course of development has at first a diameter greatly inferior 

 to that of the stump remaining in place. 



If growth proceeds rapidly, as is most usual, and if no 

 turgidity of the limb-rudiment shows itself, the latter, by 

 reason of its flaccidity, is incapable of pressing with any force 

 against the thin cuticle covering over the cut surface. 

 It is only able to distend it slightly in order to obtain neces- 

 sary room for itself. Under these circumstances it is obliged 

 to coil upon itself while remaining covered by the cuticle, 

 which forms a kind of protecting sheath. 



If, however, on the contrary, turgidity shows itself from 

 the beginning of growth, the rudiment of the limb in process 

 of formation, instead of being obliged to coil itself, is able to 

 push before it the thin cuticle endowed witii very considerable 

 elasticity. In this case nothing hinders rectilinear growth. 

 The cuticle in question can even mould itself in a more or less 

 perfect way upon the growing limb, and remains until the 

 time of the next moult. It is then cast off with the old 

 chitinous covering of the body, with which it is intimately 

 connected. 



To epitomize the question, the development of the limb will 

 follow the spiral or tlie rectilinear form, according as there is 

 fiaccidity or turgidity of the rudiment of the limb being re- 

 placed at the beginning of its formation. 



111. — tSo far as insects are concerned [Mantid^, Blattidai'^, 

 and Orthoptera saltatoria], regeneration of a part of the limb 

 alter artificial severance most often takes place by means of 

 the spiral manner of growth. I have nevertheless found some 

 exceptions which can be explained easily enough also and 

 considered as a particular case of the more usual process. 

 'I'hus, among the Phasmidpe, whilst a limb amputated by 

 self-mutilation regenerates itself according to the method 

 involving spiral growth, the regeneration of part of a limb 



* Cf. II. H. Biiuclley, ' Ou ceitain Characters of Eeproduced Ap- 

 pendages in Arthropoda/ p. 9 (1898). 



