ii6 The Method of Ovipositing. 



than the ^zz, as may be seen by referring to the 

 diagrams in Plate III, where the eggs and ovipositors 

 are all taken from photographs, and are drawn of the 

 same amplification. It follows therefore that one end 

 of the ^%% cannot be sunk in the plant tissue while the 

 other is still in the canal, and the explanation of Hartig 

 consequently fails. 



Besides, it is not possible that the whole ^^'g could 

 be received into the ovipositor and could glide through 

 it, for the ovipositor cannot be compared to a hollow 

 tube. It consists, as already stated, of three parts which 

 are firmly connected with each other. The upper is the 

 ridged seta, on the under surface of which the two spiculae 

 are mortised by two tenons. The seta certainly en- 

 closes a central cavity, but it has no connexion with the 

 canal, and merely serves to contain a nerve branch, an 

 air vessel, and some sanguineous fluid. Therefore the 

 ^g'g cannot pass through the ovipositor in the way 

 Hartig supposed. On the other hand, there is sufficient 

 space between the two spiculae to admit the egg-stalk. 



It is still difficult to understand how the ^g% is finally 

 protruded into the bud. We can clearly recognize the 

 movements of the ovipositor made by the fly, but we are 

 unable to follow the movements of the ^%%^ and only in 

 one way do we get any knowledge of this part of the 

 operation. Neuroterus laevtusculus requires from fifteen 

 to twenty minutes for the act of ovipositing. If a prick- 

 ing fly were fixed in position, by being suddenly dipped 

 into chloroform or ether, and the bud were opened, we 

 could then see how far the ovipositor had penetrated, 

 and whereabout the Qgg was : and if, during the fifteen 



