460 



SCIENCE. 



[N. S. Vol. I. No. 17 



the terebra is worked. The structure of the 

 ovipositor is well known and its parts 

 homologize with those of the same organ in 

 all Hymenoptera. It consists of a large 

 bristle or seta, and of two spiculae which 

 mortise into it by means of two tenons and 

 form the channel down which the egg passes. 

 The seta occupies half the area of a trans- 

 verse section of the terebra, and the two 

 spiculae occupy the other half. The seta 

 has a central canal which contains an air 

 vessel, a nerve branch and some san- 

 guineous fluid. While appearing like a 

 single piece, it is in reality double or com- 

 posed of two parts which, indeed, are sepa- 

 rated at the extreme base, but otherwise 

 firmly soldered together. The spiculge are 

 serrate or notched near the tip, and the seta 

 often ends in a slight hook. The two spiculse 

 play by means of strong basal muscles, lon- 

 gitudinally up and down on the tenons of 

 the seta. 



The eggs of Cynipidse are characterized 

 by having a stalk or pedicel of varying 

 length according to the species, the egg-body 

 proper, according to Adler, being at the 

 apical or anterior end which first issues 

 from the body, and the posterior end being 

 also somewhat enlarged or spatulate. In 

 repose the ovipositor is concealed within 

 two sheaths, but in oviposition, according to 

 Hartig's views, the spiculse grasp the egg- 

 stalk and push it to the tip, the fluids in the 

 egg-body being pressed back in the oper- 

 ation, so that they come to be distributed 

 along the stalk or to lie at the opposite or 

 posterior pole of the stalk. The spiculse 

 then slightly separate at the tip from the seta 

 and extend beyond it so that the apical end 

 of the stalk becomes free. N"ow by pres- 

 sure the fluid at the posterior end passes 

 back through the stalk into the opposite or 

 apical end which is plunged in the plant, 

 the basal portion becoming emptied, the 

 swollen apical end thus x-emaining in the 

 plant when the ovipositor is withdrawn, fill- 



ing the distal end of the puncture, which is 

 somewhat enlarged. The empty basal sack 

 of the egg and a portion of the stalk are 

 often left exposed, looking not unlike the 

 empty egg of some lace-wing flj' (Heme- 

 robiid). 



In short, Hartig's view, very generally 

 adopted, was that the extensile and ductile 

 egg was driven through the ovipositor itself 

 while this was in the plant, and that the 

 contents of the egg-body were pressed back 

 into the egg-stalk or pedicel during the 

 operation and collected in the posterior end, 

 and onljr after the apical end had reached 

 the bottom of the puncture did these con- 

 tents stream back into it. Adler would re- 

 fute this view and draws attention to his 

 own figures on Plate 3, where the eggs and 

 ovipositor are illustrated side by side, all 

 taken from photographs and drawn fi'om 

 the same amplification. These show that 

 the ovipositor is, in every case, longer than 

 the egg itself, the enlarged head of the egg 

 corresponding in direction to the tip of the 

 ovipositor. He argues from this fact that 

 one end of the egg cannot be in the plant 

 tissue while the other is in the canal. He 

 further argues that it is not possible that 

 the whole egg can be received into the ovi- 

 positor and glide through it in the waj' in 

 which Hartig supposed. The oi^eration of 

 oviposition according to his observations 

 consists of three distinct stages: (1) The 

 canal in the plant is first bored, after which 

 the fly rests; (2) the egg is then passed 

 from the ovarium to the entrance or base of 

 the ovipositor, the anterior sivollen end or egg- 

 body hanging out, since it is too large to be 

 passed down the channel. It is then pushed 

 along by means of the egg-stalk behind be- 

 ing grasped between the two spiculse. (3) 

 Finally, when the egg-body reaches the 

 perforation, the ovipositor is partially witli- 

 drawn and the whole egg is then puslied in 

 till the egg-body reaches the bottom of the 

 punctui-e. Adler rightly expresses wonder 



