STUDIK8 ON THE ARACHNID ENTOSTERNiTE. 225 



Studies on the Arachnid Entosternite. 



By 



R. I. Pocock. 



With Plates 13 and 14. 



The investigations here recorded were set on foot in the 

 first instance with the purpose of settling certain contra- 

 dictions as to matters of fact in the extant descriptions and 

 published ligures of the entosternites of various Arachnids, 

 which a preliminary dip into the literature revealed. It was 

 necessary to ascertain whether these discrepancies were 

 attributable to a natural variability in the organ^ to specific 

 or generic differences between the species dissected, or to 

 errors of observation on the part of the dissectors. In some 

 caseS; toO; there was an entire lack of agreement on the part 

 of observers in the interpretation of the facts recorded ; and 

 the suggested homologies between the constituent parts of 

 the entosternites of various species did not, on a priori 

 grounds, appear to be in all cases satisfactory. I was 

 anxious, moreover, to test the respective claims to recogni- 

 tion of the two theories of the origin of the entosternite 

 that have been put forward. 



I have made no examination of this organ in the Palpi- 

 gradi, Pseudoscorpiones, Podogona, Opiliones, or Acari, 

 and have nothing to add to what has already been said about 

 the entosternite of these orders. 



The contents of this essay, which deals exclusively with 

 the remaining existing orders, may be tabulated as follows : 



VOL. 46, PART 2. NEW SERIES. P 



