1897.] OF THE LEGS IN THE BLATTID^. 907 



necessary to state that at first the frequent occurrence of the 

 abnormal tarsus encouraged a belief that it was a congenital 

 variation. This was supported by several features of the case 

 besides the above. It happened by chance that individuals of 

 P. americana were examined first. Among these there were several 

 cases where one tarsus of a pair was normal, and the other 

 abnormal; and in these cases the tarsi were of approximately 

 equal dimensions and seemed symmetrical till closely examined. 

 Moreover, as shown by Table B, the abnormaUty occurred with 

 distinctly greater frequency among females than males. 



Finally, the abnormal tarsus was found in three individuals of 

 S. orientalis only -4 cm. in body-length, which is the average size 

 of newly-hatched young. 



These facts offer material for discussion, but they must be left 

 for awhile, as the evidence they afford in favour of congenital 

 origin of the four-jointed tarsus seems rebutted by that 

 subsequently obtained — that the abnormality is the form assumed 

 by the tarsus when it is a reproduction taking the place of a lost 

 or injured tarsus. 



Cockroaches, like other Orthoptera, attain sexual maturity after 

 performing a series of ecdyses, which in some species probably 

 extend over several years. The power of reproducing lost 

 appendages is known to be possessed by members of several of 

 the tribes of Orthoptera. Among the Blattidaj the reproduction 

 of the antennae of the Cockroach after amputation was first described 

 by Heineken ^ 



The evidence given below appears to establish that the four- 

 jointed tarsus arises in connection with the reproduction of the 

 leg when any part thereof has been lost or severely injured during 

 the immaturity of the animal. 



(a) Absence of abnormal tarsi in newly -hatched individuals. 



A number of egg-cases of S. orientalis were collected and 

 artificially incubated, from which altogether 210 young were 

 hatched. In a few cases limbs were found to have been 

 broken off, but all the tarsi of entire limbs were normal. 



(b) Uelutive infrequency of abnormal tarsi in very young 

 individuals. 



That there was a smaller proportion of abnormal tarsi in 

 young than in adult individuals is shown by Table B. This 

 led to an examination of young of different ages, with the 

 following result : — 



388 immature P. australasice. 



1 " ObserTations on the Eeproduction of the Members in Spiders and 

 Insects," Zool. Journal, 1829, iv. p. 425. 



60* 



