PHYSIOLOGY. 277 



a time, and through so many generations, as 

 almost to exceed belief. ( Vide page 31). This led 

 DR. HAIGHTON to entertain the opinion that 

 actual contact betwixt the male sperm and the 

 egg was not necessary, but that impregnation was 

 effected by some unknown sympathetic influence. 

 MESSRS. KIRBY and SPENCE have recourse to the 

 old doctrine of an aura seminalis being all that 

 is required to vivify the egg, and which they think 

 may be retained for a long period. Upon this 

 subject I have entered at some length in page 

 25 et seq. The ovipositor places the eggs in 

 their appropriate situations, and is an instrument 

 of most curious structure. It consists of a long 

 tube, or rather several tubes, retractile within 

 each other, like the pieces of a telescope, and 

 serves not only to convey the extruded eggs to the 

 place of their destination, but acts also as a sheath 

 for the sting, having a sharp point which makes 

 the first impression when the creature intends to 

 use its sting, indeed it appears to be itself the 

 sting. It has a slit near its extremity, through 

 which the sting and poison are allowed to pass 

 at the time of stinging. Some insects have occa- 

 sion to bore a hole in wood, or other hard sub- 

 stances, to obtain a proper nidus for their eggs ; 

 the ovipositor is their operating instrument, and 

 will either saw or bore a passage to the desired 

 place. Thus it appears that this curiously com- 



