462 



SCIENCE. 



[N. S. Vol. I. No. i; 



method of oviposition from that described 

 by either, in that the fluid egg-contents are 

 not passed from one pole to another rapidly 

 in the act of oviposition as described by 

 Hartig, but very gradually, the process not 

 being completed till just before the hatch- 

 ing. I had the assistance of Mr. Th. 

 Pergande in carefully watching the steps in 

 this particular case (in April 1884) and 

 have put them on record here for the first 

 time. Again, a small black wingless species 

 {Biorhiza nigra Fitch, subsequently described 

 as B. politus by Bassett), is not infrequently 

 found during winter under the shelter of 

 bark scales and oviposits during late winter 

 in the terminal buds of Quereus alba and Q. 

 obtusiloba. The ovipositor in this case, as in 

 most cases where eggs are laid in dormant 

 buds, is thx'ust down between the bud-scales 

 until it reaches the soft latent cell tissue 

 toward the center of the bud. And here it 

 is easy to observe, by removing the scaly 

 coverings, as I have done, that the pedicel 

 or stalk only is inserted in the embryo leaf- 

 tissue and that the enlarged portion or egg- 

 body is at first external, being pressed and 

 somewhat flattened by the surrounding leaf- 

 scales.* 



In still a third case of a small black in- 

 quiline (Cero];)tus politus Ashm..^ oviposition 

 was observed by Mr. Pergande in the mid- 

 rib of Quereus rubra, May 20, 1894 ,and in 

 this case, as my notes show, the egg is 

 thrust down iuto the puncture made by the 

 terebra in the mid-rib until not a vestige of 

 the egg is visible, the pedicel being very 

 short. 



There is, therefore, good reason for be- 

 lieving that oviposition in these insects fol- 

 lows no uniform system, and there is a 



*This fly produces an undescribed vesicular bud- 

 gall from -which issues a small black winged bisexual 

 species {DryopMnta vesieuloides M S. mihi). The gall 

 produced by this and from which the apterous agam- 

 ic generation comes is not yet known, though it mil 

 probably be a leaf-gall similar to that of Acraspis eri- 

 nacess Walsh. 



serious question whether Adler's rejection of 

 Hartig's views are justified. In connection 

 with Adler's views as to oviposition, he con- . 

 eludes from his own studies that the main 

 purpose of the egg-stalk is to supply oxygen 

 to the egg-body in the plant-tissues, but that 

 this is also an erroneous conclusion is. I 

 think, made manifest by some of the facts 

 just stated. That the function of the egg- 

 stalk is, rather, to facilitate the otherwise 

 dif&cult mechanical operation of the passage 

 of the egg down a narrow and elongate ovi- 

 positor in the manner indicated by Hartig 

 is supported by the fact that the puncture 

 is often closed at its mouth as also from 

 what we know of the similar oviposition in 

 other orders of insects. The facts, for in- 

 stance, connected with the oviposition of 

 Pronuba yuccaseUa, where the egg is thrust 

 deep into the ovarian cavity of the Yucca 

 pistil bear out this view. The egg, in this 

 case, as it passes down the ovarium has not 

 a definite pedicel or stalk, but becomes a 

 mere thread in passing through the ovi- 

 positor (the nature of which precludes any 

 external outlet during the passage) , and the 

 fluids gradually concentrate in the apical or 

 anterior end as the embryo develops. More- 

 over, it is passed into the ovarian cavity 

 and has no connection through the pedicel f 

 mth the exterior wound which is closed 

 long before the larva hatches.* 



The great service which Adler rendered 

 in the study of the gall-flies was, however, 

 to establish the fact of alternate generation 

 in so many cases. He thus proved the ex- 

 istence of alternate generation in the follow- 

 ing species : (See opposite page.) 



The writer established, by breeding, the 

 connection of the agamic Callirhytis operator 

 O. S. and C. qpemtoZa Eiley in 1872, the facts 

 and specimens having been communicated to 



* Vide the Yucca Moth and Yucca Pollination, by 

 Cliarles V. Riley (from the Third Annual Report of 

 the Missouri Botanical Garden). Issued May 28, 

 1892. 



