NO. 3 EMBRYOLOGY OF FLEAS KESSEL J\ 



Fig. 21. Transverse section through the germ band of a Nosopsyllns fasciatus 

 egg at the level of one of the pairs of coelomic sacs (CS). The 

 epineural sinus is also shown, forming as a space between the 

 embryonic band and the receding yolk mass. X 400. 



Fig. 22. Transverse section through the procephalic lobes of a Ctenocephalides 

 felis embryo showing details of the anterior region of the amniotic 

 cavity together with the cellular nature of the amniotic and serosal 

 membranes which cover it. X 450. 



Fig. 23. Portion of a sagittal section through a Ctenocephalides felis egg with 

 the anterior amnio-serosal fold beginning to form. The anterior 

 mesenteron rudiment, at a stage a little later than that shown in 

 figure 15, may be seen to the left of the fold. X 400. 



Fig. 24. Transverse section through a Ctenocephalides felis embryo just prior 

 to dorsal closure. The cells of the third dorsal organ may be seen 

 sinking into the vitelline mass. At the left a portion of the definitive 

 body cavity is evident. This section is at a stage similar to that 

 shown in figure 79. X 450. 



Fig. 25. Portion of a sagittal section through a Ctenocephalides felis egg at a 

 stage a little later than that shown in figure 54. The amniotic mem- 

 brane with its attenuated cells, the anterior mesenteron rudiment, the 

 ectoderm, and the mesodermal layer are all clearly shown. X 400. 



Plate 3 



Fig. 26. Parasagittal section of a Ctenocephalides felis embryo during the fifth 

 day of development showing the body curved ventrally. At this 

 plane the supraoesophageal and suboesophageal ganglia are con- 

 nected by one of the circumoesophageal connectives. The ganglionic 

 thickenings of the ventral nerve cord are no longer evident on the 

 surface. X 100. 



Fig. 27. Horizontal section through a portion of the ventral nerve cord of a 

 Ctenocephalides felis embryo showing the paired ganglia fused to 

 form definitive ganglia. In two of these ganglia the two cross- 

 commissural neuropile tracts are demonstrated. The interganglionic 

 connectives are also shown. X 450. 



Fig. 28. Portion of a transverse section through a Nosopsyllus fasciatus embryo 

 showing a tracheal invagination in longitudinal section. X 450. 



Fig. 29. Portion of a sagittal section through a Ctenocephalides felis embryo 

 cutting the proctodaeum in longitudinal direction. This stage is a 

 little later than that shown in figure 35. X 450. 



Fig. 30. Section along a tracheal invagination of Hystrichopsylla dippici show- 

 ing two large oenocytes lying adjacent to its wall. In this section a 

 metastigmatic invagination parallels the tracheal invagination for 

 a short distance. X 300. 



Fig. 31. Transverse section showing a portion of the head of a late embryo 

 of Hystrichopsylla dippici. The developing hatching spine is a 

 prominent structure. X 250. 



Fig. 32. Transverse section through the proctodaeum of a Nosopsyllus 

 fasciatus embryo showing the four developing malpighian tubules. 

 X400. 



