in Course of Regeneration in Arlhropoda. 315 



as the mutilated antcnnaj of the same crustacean i^row in a 

 spiral until the Hist moult after the injury. 



The dilTerence between the two modes of growth is not so 

 great as at rtrst might be imagined. Let us see in wiiat it 

 consists. In Artlirt^])ods showing spiral growth, as in those 

 wljich ))resent 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 ^vhole surtace of the cut, but near the central |):irt, 

 and growtii is generally much more rapid in length than in 

 diameter, with the residt 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 lorms a kind of ])rotecting 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 with 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 wiiich it is intimately 

 connected. 



To epitomize the question, tlie development of the limb will 

 follow the spiral or the rectilinear form, according as tiiere is 

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

 placed at the beginning of its formation. 



III. — tSo far as insects are concerned [Mantida?, Blattida^*, 

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

 alter artijicial 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. 

 1'hus, among the Phasniid.'e, whilst a liu)b amputated by 

 self-mutilation regenerates itself according to the method 

 involving spiral growth, the regeneration of part of a limb 



* (/. II. II. IJrindlty, 'On ceitain Characters of Keproduced Ap- 

 pendages in Arthropuda,' p. 9 (lt<l>s). 



