terminal segment in some male Hemiptera. 423 



little doubt, however, that this segment is capable of 

 being so extended, for it is by such an extension that I 

 presume the process of coupling to be rendered possible. 

 Still, there are other considerations that make it difficult 

 to believe that in these Tesseratomince and ScutelleriiKS 

 the alimentary canal can have become shortened by a 

 process of evolution. Without referring to these more 

 particularly at i^resent, 1 will content myself with saying 

 that it appears more probable that the original termina- 

 tion of the genital segment was at the line of the 

 diaphragm, and that the part posterior to this — that is, 

 the posterior chamber, in which the external male parts 

 are situated — is a subsequent growth that has taken 

 place pari passu with the evolution of the male parts for 

 the purpose of their protection. If so, then both the 

 posterior chamber and the peculiar modifications of the 

 rectal-cauda are to be lookod on as having as their 

 objective result the protection of the cedeagus. 



With reference to the special function of the lateral 

 appendages and the inferior process, I can only make 

 vague suggestions which actual observation may probabl}' 

 prove to be erroneous. Where the inferior process is 

 specially developed, it perhaps determines the exact 

 direction the cedeagus shall take when it is defiexed. 

 The function of the lateral appendages is at present 

 more obscure, but they are always present, and probably 

 play an important part in the act of copulation. I have 

 stated that they are connected together by a powerful 

 ligament pressing on the back of the theca of the 

 cedeagus, and, on breaking up a specimen of Eustheiies 

 pratti, I find that this is just at the spot where the 

 ejaculatory canal passes into the theca ; it is therefore 

 quite probable that the lateral appendages have a con- 

 trolling power over the passage of the seminal fluid. 



I see no reason for considering, with any great proba- 

 bility, that any part of the structures are clasping or 

 holding instruments, I look on them as (1) for pro- 

 tection of the sensitive parts from pressure, (2) for the 

 exclusion of parasites, (3) as directing instruments to 

 determine the exact direction of movement of the true 

 intromittent organs, and (4) as probably instruments 

 for altering the pressure on the ejaculatory canal at its 

 point of entrance into the cedeagus ; but the superior 

 lateral processes, which are only present in some species, 



