Waite. — Antennal Glauds. 



PLATE 2 



(In Figs. 15-17 anterior is up on the plate ; in Figs. 18-24 (except 23) dorsal is 

 up ; in Fig. 23 lateral is up; in Figs. 18, 20, 22,24, anterior is to the right ; in Figs. 

 19, 21, 23, anterior is to the left ; in Fig. 25 mediad is to the right. In Figs. 18-25 

 the mesoderm is distinguished by the darker shade.) 



Fig. 15. Ventral view of an embryo 15-17 days after extrusion of egg. X 72. 

 Fig. 16. Similar view of an embryo 16-18 days after extrusion of egg (stage at 



which gland first appears). X 72. 

 Fig. 17. Similar view of an embryo 23-25 days after extrusion of egg. X 72. 

 Fig. 18. Part of parasagittal section through second antenna of embryo 15-17 days 



old, showing undifferentiated mesoderm in axis of antenna. X 410. 

 Fig. 19. Similar section of embryo 16 to 18 days old (Fig. 16), showing (in the 



mesoderm) first differentiation of endsac with two nuclei. X 410. 

 Figs. 20-22. Parasagittal sections through antenna at slightly more advanced 



stages. (Fig. 20 is youngest, Fig. 22 oldest.) X 410. 

 Fig. 23. Section inclined slightly to the frontal plane at a stage when the endsac 



is ovate in form and contains in all 12 nuclei. X 410. 

 Fig. 24. Parasagittal section through antenna in which a vacuole appears in the 



endsac. X 410. 

 Fig. 25. Anterior face of a transverse section through right antenna at stage when 



invagination of ectoderm first begins. (Embryo 28-30 days old.) 



X 410. 



