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Show 1897.] OF THE LEGS IN THE BLATTID^B. 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. A m oner 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 abnormality 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 ecclyses, 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 Blattidae the reproduction of the antenn se 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) Belutlve infrequency of abnormal tursl In very young Indlvlduuls. 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. australuslce. Percentage Body-length. with abnormal tarsi. Under 1*05 cm. 10*7 1-05 to 2*0 cm. 20*0 2*05 to 3*0 cm. 25*0 1 "Observations on tbe Eeproduction of the Members in Spiders and Insects," Zool. Journal, 1829, iv. p. 425. 60* |
