11)09.1 



NATURAL SCIENCES OF PHILADELPHIA. 



!19 



Col., colulus. 

 Cr., cribellum. 



Cr. PL, spinning plate of cribellum. 

 Ect., ectoblast. 

 H., heart. 



L. 1-L. 4, ambulatory limbs 1-4. 

 L. 1 G.-L. 4 G., ganglia of the pre- 

 ceding. 

 Lam. 1, primary lamella of lung-book. 

 Lam. 2, secondary lamella of lung-book. 

 -1/., muscle. 

 Mes., mesoblast. 

 M. Sp., median spinneret. 

 -V. C, nerve cord. 



P. Cav., ectoblastic cavity of mng- 

 book. 



Pea 1 ., pedicel of abdomen. 



P. Sp., posterior spinneret. 



P. St., pulmonary stigma. 



Pal., lung-book. 



R. B., rectal bladder (stercoral pocket). 



Ros., rostrum. 



Sp., spinneret. 



Sp. GL, spinning gland. 



Tr., trachea. 



T. St., tracheal stigma and vestibulum. 



x., ectoblastic thickening of undeter- 

 mined significance. 



Plate XI. — Theridium tepidariorum. — Oblique longitudinal sections through 



the lung-book region, all drawn to the same scale. 

 Fig. 1.— About 98 hours. 

 Fig. 2. — About 127 hours. 

 Figs. 3, 4. — 121 hours; fig. 3 through the stigma, and fig. 4 somewhat 



lateral to it, of the same lung-book. 

 Fig. 5. — Of another embryo of 121 hours. 



Fig. 6. — Of another embryo of 121 hours, to one side of the stigma. 

 Fig. 7. — 145 hours. 

 Fig. 8. — 145 hours. 



Plate XII. — Theridium tepidariorum. — All the figures except 16 drawn to the 



same scale. 

 Fig. 9. Longitudinal section of lung-book, about 150 hours. 

 Fig. 10. — Oblique cross-section of lung-book of an embryo of the same age. 

 Fig. 11. — Longitudinal section of a lung-book, the lamella 3 not shown in 



their full length, about 218 hours. 

 Fig. 12. — Longitudinal section through pulmonary and tracheal stigma, 



145 hours. 

 Fig. 13. — Median section of tracheal stigma, 168 hours. 

 Fig. 14. — Median section of trachea, about 218 hours. 

 Fig. 15. — Median section of trachea, 15 days. 

 Fig. 16. — Oblique dorso-lateral surface view of embryo of about 127 hours. 



Plate XIII. — Loxosceles. — Figs. 17-24 are surface views of whole-stained 



embryos drawn to the same scale, in figs. 17-19 the extra-embryonic 



area being stippled. 



17. — Postero-ventral , 190 hours (8 days). 

 Fig. 18. — Postero-ventral, 170 hours (7 days). 

 Fig. 19. — Postero-lateral, 170 hours (7 days). 



20.— Lateral, 218 hours (9 days). 



21.— Ventral. 



22. — Abdomen, ventral, 265 hours (11 days). 



23. — Abdomen, ventral, 14 days. 



24. — Abdomen, ventral, 20 days, the hypodermal hairs not drawn. 

 Fig. 25. — Median longitudinal section of the colulus of an adult, its free apex 



at the left and its dorsal surface above. 



26. — Ventral view of colulus and spinnerets of an adult female, from 



an unstained balsam mount. 



27. — Adult vestibulum and roots of main tracheal branches, caustic 



potash preparation. 



Fig. 



Fig. 



Fig. 



Fig. 



Fie 



Fig. 



Fi£ 



Fi° 



Plate XIV. — Evagrus, Filistata, Dictyna, Hyptiotes. — Figs. 28-32 are drawn 

 to the same scale. 

 Fig. 28. — Evagrus, lateral view of embryo before reversion. 



