6 Transactions of the Society. 



Let us suppose that a complete spermathcca is now before us ; 

 as we turu it we get it into such a position that its outline is not 

 unlike the back of a man's head carrying two large and prominent 

 ears. These latter are the upper ends of two glands (plate I. 

 fig. 5, a h), something less than 2U0 fj, in diameter, and which are 

 held in position by receiving very numerous twigs from the invest- 

 ing tracheal plexus. These glands passing down the opposite sides 

 of the spermatheca, meet together and form a junction 2h near 

 the spermathccal duct c. They con.-ist of nucleated gland cells 

 surrounding a tube t which runs from end to end and enlarges 

 somewhat during its course. This tube gives off thousands of 

 tubelets which pass to the distinct cells, upon the walls of which 

 they seem to expand; but after considerable painstaking I feel 

 myself uncertain upon this point. 



The spermathccal duct (fig. 5, c), which is short, stiff, and 

 slightly rugose, points towards but does not immediately join the 

 duct of the appendicular * gland. Attached to these ducts and 

 valve are five main muscles, two of which are sphincters, but very 

 faintly indicated at e and /, lest they should obscure the structure 

 of the valve before which they in reality pass, and which are 

 the main instruments for respectively and independently closing 

 the spermathecal and appendicular gland ducts. These sphincters, 

 which are separated by an intervening wedge-shaped disk m, lie 

 towards each other at an angle of from 30^ to about (JO^, and may 

 be beautifully shown by polarized light. The prisms being crossed, 

 the object is so staged that one sphincter most completely resolves 

 the polarized beam, by which every fibre in it can be perfectly 

 dissociated from its companion, which is placed at such an angle 

 that it gives no perceptible twist to the plane of polarization, 

 and 60 remains out of view. The rotation of the stage plate 

 now darkens the first observed sphincter, whilst the second be- 

 comes brightly illuminated. An indurated integument, probably 

 a chitinous plate {n in the figure), is pushed towards the sperma- 

 thecal duct by the contraction of its proper sphincter, and in this 

 woik it is aided by the muscle h, which is one of two, the ten- 

 dinous extension of which is only about 25 [jl in diameter, or 1/24 

 of the thickness of a human hair.f These muscles would, no doubt, 

 all remain tense the insect being in a condition of repose; but 

 should she be engaged in ovipositing and spermatozoa be required 



♦ This name appears to me not well chosen, but since it has been given it liad 

 better be retained, although " mucous gland of the female " would have been more 

 exi)ressive. 



f I fully feel the difficulty of interpreting a mechanism such as this, but 

 very many dissections made witli great care and most scrupulously examined, 

 will, I hope, be thought to justify the explanation given, which certainly seems 

 to me to satisfy fully both the natural history and the microscopy of the case. 



