178 Dr. T. A. Chapman 07i 



lattice girder, so as to secure much stiffness, and any 

 buckhng is prevented by the instrument being confined 

 beneath the leaf cuticle at the time when it is subjected 

 to the greatest strains. 



The saw " is curled right round the end of the guide 

 (support) and goes to and fro rapidly, without however alter- 

 ing its position. At first glance the movement is rather 

 a twinkling than a to-and-fro movement, but it is soon 

 realised that, the saw being double, one portion advances 

 as the other retreats. This is easily seen in the portion 

 between the leaf and the insect, where there is nothing either 

 in front or behind the saw. 



" The cutting is done by the margins of these two pieces 

 at the end, and advancement is rapid, steady and uniform, 

 but the actual alternating movement of the saws across 

 the line of advance is much more rapid than the actual 

 advance, perhaps four or five times as rapid." 



The penetration of the leaf is first directly inwards from 

 the edge, and during this period the cutting is done by the 

 portions of the saws that curl round the end of the supports. 

 When the terebra is engaged to its full length directly 

 inwards, it has cut a space under the cuticle just sufficient 

 to hold it, or wider by the trifling amount that the saw 

 curls round to the other side of the support. The twinkling 

 continues but the cutting is now done forwards by the 

 front margins of the saws, and continues doing so till the 

 terebra swinging forward is about parallel to the edge of 

 the leaf, with its extremity in the same direction as the 

 insect's head, and has behind it a free space or pocket 

 approximately circular. " When this position is reached 

 a short rest takes place, then, after some 10 seconds or 

 so, some movements hardly affecting the terebra, but of a 

 similar but rather slower and more heaving character 

 than when cutting is being done, take place more in the 

 body of the insect than in the terebra. This is hardly 

 noticed before the egg begins to occupy the saw, which 

 resumes movements similar to those used in cutting and 

 which probably assist the advance of the egg between its 

 right and left portions, which must now be separated 

 enough to admit of its passage, though the distension is 

 too slight to be observable. " The actual egg when laid 

 is a fairly large and thick oval body that occupies 

 practically the whole pocket. In the actual laying the 

 appearances seem to compel one to believe that in its 



