LIST OF ILLUSTRATIONS. 
PLATES. 
PaGE 
Piste ia Piges of certain) Drosophilmce 300 ah a ea 8 aN Vy ea ae 18 
2. Scaptomyza adusta, male; Drosophila busckii, male; Drosophila funebris, 
64 
PETES RN ae ac crete a naa Siac 30 SUC IL Lane a Bs Pais eRe ML AUS 3 
3. Drosophila immigrans, male; Drosophila melanogaster, male; Drosophila me- 
Ramied, Lemialers scsiede none, 6h hc ek del ak Male nag Ay hee Cc, Sw A 84 
TEXT-FIGURES. 
PaGE 
Fig. 1. Anterior spiracle of third-stage larva of Drosophila funebris............... 20 
2. Cephalopharyngeal skeleton of third-stage larva of Drosophila melanogaster. 21 
3. Cephalopharyngeal skeleton of third-stage larva of Drosophila funebris. ... . 21 
4A, Cephalopharyngeal skeleton of third-stage larva of Scaptomyza adusta....... 21 
.5. Wing of a newly emerged Drosophila simulans that has not yet unfolded..... 23 
ead ‘of Drosophilayrobusta:s. .osc.c dag Le ie ee 25 
‘7. Side view of thorax of Drosophila funebris (diagrammatic)................ 27 
So Manor MUrosopulla melanogaster...) 04 s)aos le ded ae meee ne ee ee 29 
ONO: fe (Ovi OSibOr IAteS: uid ces ds eines Oe kha hee eae OE ren ee 32 
as, alo iG External male Genitalia sos co sid as che, 5 oelerde ates ae eee 34 
17. Oblique section through spermatheca of Drosophila obscura, showing sperm 
TEAVST YG Pe RD ie ON AN NER n a a eT ACRE Dae AAEM RAB GEC I A i el. 35 
"18-81. Spermathecze, magnified 250 diameters... .... 0.0... 00 cece ee ee be ee 36 
102-43. Spermathece, magnified 250 diameters... .... 00.00.0602. 000e0000er nes 37 
44. Diagram of chromosome groups found in the Drosophiline (after Metz)... .. 39 
45. Headof male; Drosophilatmelanogaster': 2)... 2. .on 0 5 sso daa es eee 92 
40; aead of male Drosophila ‘simulans (20. ud ee 2k ee eee 92 
47. Drosophila obscura. Front leg of male, showing two tarsal combs.......... 93 
PASC MOTOSOP UALS WARIS POR oe 34) sos va! fiat spa anneal eee eal Bey a eo ed ae 97 
49; Drosophila ‘superba. Wing'of type specimen... .....). 2.00.22 wee ee wee 105 
iv 
