THE SOCIETY S NOTE-BOOKS. 



63 



Fig. 7- 



Fig. 8. 



scabbard or sheath." The annexed diagram 

 (Fig. 6 '^) gives a rough representation of these 

 organs. Between them the dark point of the 

 dart, with the spicule projecting therefrom, is 

 seen to protrude. The spiculae seem to arise 

 from their anterior border at a. a., as may be 

 seen in the Sand- Wasp, and travel in a curved 

 groove along their inner edges till they enter the 

 dart which lies between them. A section of 

 the dart is something like the diagram (Fig. y), 

 the two little black dots showing the position of 

 the spiculcC, which, it may thus be seen, can only 

 be forced out of their channel by violence. 

 Amongst the many curious questions which the 

 subject suggests, I have been somewhat puzzled 

 to account for the exsertion of the spiculse. 



I cannot see that they are directly acted upon by muscles, but I 

 gather from Westwood's remarks that the sting when in action is 

 bent away from its position between the sheaths, and, indeed, I find 

 by experiment it is capable of being bent at a very considerable 

 angle, as may be seen by the annex- 

 ed diagram (Fig. 8), which is a side- 

 view of what I believe to be the yth, 

 8th, and 9th segments of the abdo- 

 men, forming the sexual organs. 

 '^ d. Y d. is the seventh, S d. the 

 eighth, and g d. the ninth dorsal 

 plate, st — also marked p v, the dart 

 or ventral plate — showing its posi- 

 tion in repose, s. t' . the same in 

 action, 8 d.ap. the eighth dorsal x'^'^^-==^7 

 appendages, sh. or g d.ap. the sheaths or ninth dorsal append- 

 ages, X y the basal part of the spicules. 



By the above diagram, it may also be seen that in the position 

 of repose, the terminal portions of the spiculee from the point y to 

 the termination of the sting are bent at a considerable angle to 

 their basal portions, x y, but that Avhen the organ is called into 

 action, as seen by the dotted portion of the figure, the course of 

 the spiculse is much straightened, and I think that this straighten- 

 ing and consequent shortening of their course is one cause of their 

 exsertion, which would be thus brought about by the same 

 muscular act, which bends the whole organ from its original 

 position. Nevertheless, I think it not improbable that some other 

 means may be provided for imparting an independent and alter- 



* These drawings are from a dissection of the insect I made for the purpose. 



