1898.] APPENDAGES IS THE AETHEOPODA. 925 



any point from the femoro-trochanteric suture downwards is 

 followed by the reproduction of the lost parts, with the dis- 

 tinguishing feature that the tarsus consists invariably of only 

 four joints, the normal congenital tarsus possessing five. The 

 present paper is concerned with the structure of the four-jointed 

 tarsus of reproduction, and with cases of reproduction of 

 appendages in other Arthropods with which it possesses certain 

 features in common. In this connection it is desirable to make 

 some reference to the condition of our knowledge of the repro- 

 duction of appendages among Arthropods geuerally. The literature 

 of the subject does not seem to be extensive. Thirty years ago 

 Milne-Edwards (59) summarized the work then published, and 

 since that time the subject has received only sparse attention, 

 especially from the standpoint of experiment. But certain facts 

 have received satisfactory demonstration. [Among Arthropod 

 animals reproduction is always confined to the appendages. 

 Eeproduction of portions of the trunk, as is common in the 

 segmented worms, appears never to occur.] 



The Period of the Liee-histoey dtjeing which Eepeoduction 

 OF THE Appendages can occur 



appears to be coincident with that of the ecdyses. Hence 

 in Crustacea and Myriapoda the power of reproducing the 

 appendages continues after the attainment of sexual maturity, 

 while in Arachnida and Insecta it ceases with the completion 

 of the post-embryonic development. But in view of the little 

 that is known of the life-histories and ecdyses of Thysaum'a, 

 CoUembola, and some Orthoptera, the above statement must be 

 made with some reserve as regards the Insecta. It is, however, 

 certain that in the case of most of the groups no repro- 

 duction of appendages can occur after sexual maturity has heen 

 attained, either through a series of ecdyses or on emergence 

 from a pupal state. As regards Peripatus, Mr, Adam Sedgwick 

 kindly informs me that he knows of no instances of reproduction 

 of any of the appendages, or of any cases in which an appendage 

 presented features suggesting that it had been reproduced. 

 If regeneration does occur in this isolated genus, a knowledge of 

 its features would be of special interest. 



The Paets of an Appendage feom which Eeproduction 

 can commence. 



If an appendage is wholly removed from the body it seems 

 that reproduction never occurs. Thus in a crustacean the coxo- 

 podite of an appendage, in an insect the scape of an antenna 

 or the coxa of a leg, must be left intact if there is to be reproduction 

 of the extremity. An appendage is therefore never reproduced as 

 a whole by the trunk, but the event is realJy the formation of a 

 new extremity by a larger or smaller basal portion. Accidental 

 n jury to an appendage may theoretically involve any degree of 



