ON THE OOCYTES OF THE GALL-FLY NEUROTERUS. 327 



On certain Nuclear Phenomena in the Oocytes of I he Gall-fly Neuroterus. 

 By Lancelot T. Hogben, B.A., B.Sc. (formerly Frank Smart Prizeman 

 in Zoology, Cambridge). (Communicated by Dr. E. Drabble, F.L.S.) 



(With two Text-figures.) 

 [Read 6th November, 1919.] 



Despite the existence of a very considerable literature dealing with insect 

 cytology, there is still the most meagre knowledge of the history of the 

 nucleus in the oocyte, particularly in the case of the Hymenoptera, though 

 this group has attracted many investigations of a cytological nature on 

 account of the frequent occurrence of parthenogenesis among its members. 

 Recent work by Doncaster on the process of maturation, and by Hegner, 

 Martin, Silvestri, and Gatenby on the earlier stages of oogenesis in certain 

 of the Hymenoptera parasitica, have revealed somewhat unique phenomena 

 which call for further elucidation. The present communication contains 

 some observations of a preliminary nature which shed light upon the 

 character of the mitotic figures which occur during the formation of polar 

 bodies in this group. 



Gametogenesis in the Gall-fly Neuroterus has already been made the 

 subject of three memoirs by Prof. Doncaster, to whom I am indebted for 

 the material of the present note. In describing the maturation of the ova, 

 attention was directed to the fact that an unique type of ookinesis occurs, 

 in which, to quote Doncaster, " the first division takes place by the drawing 

 out of threads (probably double) on each side of the nucleus ; the reticulum 

 becomes absorbed in these threads, which form two groups of parallel 

 chromosomes on a spindle. These chromosomes then divide, probably 

 longitudinally, giving rise to the group which forms the egg and three polar 

 groups of chromosomes." An apparently similar type of maturation division 

 was described nearly twenty years ago by Henking in the Cynipid genus 

 Rhodites. Quite recently Hegner and others mentioned above have made 

 cursory references to the existence of a precocious maturation spindle of a 

 normal type in certain species of Chalcids, Braconids, and Cynipids ; and, 

 according to these authors, instead of proceeding to pass into anaphase, the 

 chromosomes, in the form of end-to-end pairs, condense into a compact 

 nucleus like that found in the full-grown egg of Rhodites and Neuroterus. 

 It was therefore thought desirable to attempt to correlate these phenomena 

 if possible. 



Oocytes of the agamic generation were chosen for study, the larvae of the 

 spring brood being entirely females. A few pupse of Neuroterus lenticularis 



