276 AYERS ON THE DEVELOPMENT 



and ventral body-walls. The embryo is now head uppermost and faces in the opposite direction to 

 what it did before revolution. It requires about 24 hours with a temperature of 70° F. to accomplish 

 the change. 



Fig. 11. Micropylar end of the living egg in its natural condition. X 125. 



Fig. 12. Germinative vesicle of Oecanthus in which the nuclear membrane has been ruptured by the 

 dissecting needle. From an acetic acid, glycerine preparation. X 560. 



Fig. 13. Surface view of the follicular epithelium of an ovariolc of Acheta prepared in silver nitrate. 

 X 560. 



Figs. 14-17. Surface views of the follicular epithelium of an ovariole of Oecanthus, from successive 

 follicles, illustrating yolk formation by nuclear degeneration. X 560. 



Fig. 18. Segment of a section of an ovariole of Acheta abbreviata. Prepared in gold chloride, glycerine. 

 X 560. 



Fig 19. Nuclei in process of division from the follicular epithelium of Acheta. The ovariole was pre- 

 pared in gold chloride, alcohol, balsam. X 560. 



Fig. 20. Follicular epithelium from an ovariole of Acheta abbreviata prepared in gold chloride and 

 glycerine. X 300. 



Fig. 21. Optical section of the membranes of a fresh egg; 0, blastoderm; 1, vitelline membrane; 

 2, inner-chorion ; 3, outer-chorion. X 400. 



Fig. 22. Frontal view of the brain in situ, showing the outgrowing nerves. X 50. 



Fig. 23. Lateral view of one of the lobes. From an embryo in clove oil. X 50. 



Fig. 24. Optical longitudinal section of the antenna of a young embryo showing the median mesodermic 

 partition. 



Fig. 25. Longitudinal section of the terminal filament, or germarium, of an ovariole of Oecanthus, from 

 an osmic acid dissection. X 600. 



Fig. 26. Longitudinal section of the germarium of Oecanthus near its junction with the vitellarium, or 

 follicular portion of the ovariole. X 560. 



Fig. 27. Optical section of the smaller part of the vitellarium of Oecanthus, from a hydrochloric-alcohol 

 preparation. X 160. 



Figs. 28, 29. Two ova of Oecanthus in which the germinative vesicle has come to the surface preparatory 

 to its disappearance. The vesicle lies in contact with the vitelline membrane. Fig. 28 X 30; fig. 29 X 25 



Fig. 30. A cell from the follicular epithelium of an ovariole of Oecanthus niveus, in which the original 

 nucleus has given rise to three others. X 560. 



Fig. 31. A serosa nucleus immediately after division. Acetic-acid carmine. X 560. 



Figs. 32 and 34. Serosa cells treated with acetic acid carmine. X 560. 



Fig. 33. Four serosa cells of Oecanthus treated with acetic acid carmine. X 600. 



Fig. 35. Endodermic or yolk nucleus in the uninjured egg; the granules were streaming in the direction 

 indicated by the arrows. X 800. 



Figs. 36, 37, 38, 42 and 44. Free cell elements from the yolk of an egg of Oecanthus in which the ger- 

 minal band was formed. They are the nuclei of yolk cells. Treated fresh with osmic acid, stained in 

 Beale's carmine, mounted in glycerine. 



Fig. 39. Three papillae broken off the micropylar cap. The central lumen tapers to a point near the ex 

 tremity of the papilla. The fine lines radiating from the lumen give it a plumose appearance. X 500. 



Fig. 40. Surface view of a papilla showing a groove on its upper surface. X 600. 



Fig. 41. Yolk nucleus. 1IC1. acohol solution, alum carmine, mounted in balsam. X 560. 



Fig. 43. Three albuminoid masses treated while fresh with 0.25 % osmic-acetic acid solution, stained in 

 picro-carmine, mounted in benzole-balsam. 



Figs. 45, 46. Lateral and dorsal views of the mandible at the time of hatching. X 65. 



Fig. 47. Surface view of the eye of Oecanthus soon after hatching, x 125. 



Fig. 48. Eight germinative vesicles of Oecanthus and Acheta, one of them from an acetic acid prepara- 

 tion, the others from gold chloride and glycerine preparations, all magnified about 300 diameters. 



PLATE XXI. 



Figs. 1, 2, 3, 4, 6, 7, 13. Serosa nuclei treated while fresh with osmic acid, stained in Beale's carmine, 

 mounted in glycerine. X 1000. 



