1909.] 



Gametogenesis of the Gall-Fly, etc. 



ill 



In conclusion, I wish to acknowledge the assistance received in the later 

 part of my work from a grant from the " Endowment of Research Fund " of 

 the Birmingham Natural History and Philosophical Society, and especially to 

 record my indebtedness to Prof. Bateson, who has read the MS. of the paper 

 and given valuable help in criticisms and suggestions. 



EXPLANATION OF PLATES. 



The figures, witli the exception of Nos. 20 and 22, were drawn with Zeiss apocliromatic 

 objective, 3 mm. (apert. 1 "40), and Zeiss ocular 12, giving a magnification of about 

 1600 diameters. When the magnification is less, it is mentioned in the description of the 

 figure. The outlines of the larger figures were drawn with camera lucida, but the 

 chromosome groups are drawn free-hand. 



Plate 1. 



Fig. 1. — Chromosome group from anaphase of mitosis in developing wing of old larva, 

 male. 



Fig. 2. — Two similar groups from female pupa, summer generation. 



Fig. 3. — Two similar groups (the two ends of one mitotic figure) from a pupa of the 

 spring generation. 



Fig. 4 a, b, c. — Three anaphases, two in face and one side-view, of spermatogonial 



mitoses, half-grown larva. 

 Fig. 5 a, b. — Two primary spermatocytes, after the growth period. Male pupa. 

 Fig. 6. — Prophase of first spermatocyte mitosis. Chromosomes appear as about 



10 irregular bands. 



Fig. 7 a. — Early stage of first (aboi'tive) spermatocyte division. A centriole is seen at 

 each end of the cell, and a small dot on the upper edge of the nucleus. 



Fig. 7 b. — Later stage : the nucleus is re-forming, and the cytoplasmic bud with the- 

 centriole is being separated. 



Fig. 7 c. — Bather earlier stage : pear-shaped nucleus and finger-like process with centrioJe 

 at its tip. 



Fig. 8 a, h, c. — Secondary spermatocytes, three stages of re-formation of the nucleus. 



In 8 6 and c the cytoplasmic bud at one end, and the stained dot near the 

 nucleus, are visible. 



Fig. 9. — Early prophase of second mitosis. More than 10 chromatin bodies are visible, 

 although part of the nucleus is not included in the section. At this stage the 

 chromatin bodies are not always so definite as in this case. 



Fig. 10 a, b, c. — Three prophases of second spermatocyte mitosis, showing 10 band-like 

 chromosomes. In 10 a not all the chromosomes are represented ; in 10 c the 

 little knob on the lower side of the cell perhaps represents the " cytoplasmic 

 bud." 



Figs. 11 and 12. — Equatorial plates of second mitosis ; in 12 the stained dot is seen 



outside the circle of chromosomes. 

 Fig. 13 o, b. — Two metaphases in side view. 



Fig. 14 a, 6. — Anaphases in side view. In each the stained dot is seen near the lower 



end of the spindle. 

 Fig. 15 a, b. — Telophases : stained dot seen included in one daughter-cell. 

 Fig. 16. — Two telophases seen in pole-view. 

 Fig. 17. — Two early spermatids. 



K 2 



