1909.] 



Gametogenesis of the Gall -Fly, etc. 



91 



Flemniing's strong tiuid, or sometimes in Petrunkewitsch's fluid ; owing 

 to their small size it was found that when the animals were well opened, 

 fixation was quite successful after half an hour in strong Flemming, and 

 if they remained too long the cells became over-fixed. The sections were 

 stained in Heidenhain's iron-hfematoxylin and sometimes in safranin as a 

 control. 



In larva', shortly before pupation, the testes contain only spermatocytes, 

 and no division-figures are found. In younger larvai it is not quite easy to 

 distinguish the sexes, but the ovaries are larger, the cells are beginning 

 to arrange themselves in strands to form the egg-tubes, and some cells are 

 larger than the rest, with very large nuclei, and presumably are developing 

 'into eggs. The testes are smaller and all the cells appear alike. They have 

 vesicular nuclei with a large nucleolus, and are much like the embryonic 

 cells of the body-tissues. I have found only one larva* which shows the 

 .spermatogonia! divisions, and these are remarkable from the large size of 

 the chromosomes and spindle, and from the fact that there are clearly 

 10 chromosomes at each end in the anaphase (Plate 1, fig. 4, a, h, c). The 

 chromosomes are elongated and rod-like, and when the spindle is cut across, 

 the number 10 can be counted with great confidence at each end. In the 

 same larva mitoses in the body-cells show clearly the diploid number 

 (about 20) ; in ihis particular larva I have found none in which I can 

 -count the chromosomes with perfect accuracy, but in many mitoses at least 

 18 can be seen without any doubt, both in metaphase and anaphase. It 

 appears, then, that while the germ-cells contain only 10 chromosomes at 

 this stage, the body-cells contain 20. In female pupte of the same age, as 

 will be described below, 20 chromosomes appear both in oogonial and somatic 

 divisions. 



In larva?, shortly before pupation, the testes are like those of young pupae, 

 'but contain only primary spermatocytes ; in some follicles these are in the 



* Since the paper was sent for publication, I have found a second young larva showing 

 10 chromosomes in the spermatogonia! mitoses both in metaphase and anaphase. I have 

 also discovered that in the developing central nervous system of male larvae (several 

 different specimens) many, but not certainly all, of the mitotic figures show the haploid 

 number of chromosomes (10). In female larvae the mitoses of the nervous system contain 

 the diploid number. I have not found any perfectly clear equatorial plate in the male 

 nervous tissue showing the diploid number, but some figures suggest it, and it is possible 

 that the supporting cells, like those of the hypodermis, have the full number, and the 

 nerve-cells the reduced. It should also be mentioned that in both sexes there occur in 

 places, in or just below the hypodermis, giant nuclei some 15 or 20 in diameter, and 

 in one female larva I have found a division figure of one of these nuclei in anaphase 

 with at least 50 chromosomes at each pole. A fuller description, with figures, will be 

 given in the second part of this paper. — November, 1909. 



