Dr. David Sharp's Studies in RhynchopJiora. 221 



it in water, and wash away the macerated portions, and 

 when this is well completed attempt the eversion of the 

 sac. This is a delicate operation and requires experience 

 and patience to obtain success. Make a minute hook by 

 turning the point of a fine needle, and then blunt this so 

 that it will catch the wall of the sac and enable a pull to 

 be made on it without penetrating or tearing the sac. The 

 difficulty is to hold the specimen without compressing it ; 

 this is best done under water with the aid of a little cotton- 

 wool. Then tease the sac out little by little from the 

 median orifice, and when it is everted take a very finely 

 pointed pipette and inject it with the water. When it is 

 restored to its natural form, it should be placed under the 

 microscope and drawn with the camera lucida at once, 

 for there is no way known to me of fully preserving the 

 shape after mounting. In the case of small specimens 

 the chances of success are much reduced, and if the median 

 lobe is a long, slender, hard tube the sac cannot be arti- 

 ficially everted. It can be cut out by splitting the median 

 "lobe, but this is of comparatively little service as it shows 

 only the wrong side of the sac. Any one who can invent 

 methods of overcoming the difficulties will be rendering a 

 great service to entomology. Specimens that have been 

 killed and preserved in spirit are not suitable for examina- 

 tion of the sac, as it never regains pliability thoroughly. 

 The time occupied by maceration can be greatly reduced 

 by heating the fluid, but without caution and experience, 

 this is likely to result in spoiling the specimen. 



I must not conclude without thanking Mr. and Mrs. F. 

 Muir for their assistance, as it is to them that the illustra- 

 tions are due. 



Description of Plate IX. 



Lettering of all the figures : — 

 8 = eighth tergite or dorsal plate. 



viii = eighth sternite or ventral plate = true last ventral. 

 an = orifice of alimentary canal. 

 cm (or im) = connecting <>r membranous area, between (1) tegmen 



and apex of body, and (2) between tegmen and median lobe, 

 ec = external cloaca. 



ej — duct proceeding from the testes (in fig. 4 the duct has dis- 

 appeared owing to reduction of the drawing). 



