j6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



Fig. 71. Sagittal section through the posterior region of the germ band of a 

 Ctcnoccphalidcs felis embryo showing the lumen of the proctodaeum 

 together with two diverticula at its inner end representing the 

 beginnings of two of the malpighian tubules. X 400. 



Fig. 72. Transverse section through the germ band of a Ctcnoccphalidcs felis 

 embryo showing the early differentiation of the ventral nerve cord. 

 The neural groove is shown at the middle of the band and to the left 

 of this groove, just below the ectoderm, several neuroblasts may be 

 seen. These neuroblasts are larger and rounder than the mesoderm 

 cells which lie below them. The elongated ectodermal cells are 

 dermatoblasts. X 400. 



Plate 10 



Fig. 73. Whole mount of a Ctcnoccphalidcs felis embryo dissected from the 

 egg after 3 days of development, when withdrawal of the tail from 

 the deutoplasm is complete. Both the anterior and the posterior 

 extremities of the germ band have grown around their respective 

 poles of the egg and approximate each other on the dorsal surface. 

 The segmentation is distinct. X H5- 



Fig. 74. Parasagittal section of a Ctcnoccphalidcs felis embryo at a stage 

 similar to that shown in figure 73. Segmentation is distinct. The 

 oral appendages appear in order : labral, mandibular, maxillary, 

 and labial. Because of the parasagittal plane of the section, the 

 stomodaeum does not show, and on the maxilla is an apparent 

 ventral projection. A deep cleft separates the maxilla from the 

 labium. The three thoracic segments follow the labium and posterior 

 to these come the abdominal segments. The eleventh abdominal 

 segment has already been carried in from the surface by the 

 invagination of the proctodaeum. X lI 5- 



Fig. 75. Sagittal section through a Ctcnoccphalidcs felis embryo at a stage 

 corresponding to that shown in figures 73 and 74. The stomodaeal 

 and proctodaeal invaginations are clearly shown. The labrum lies 

 anterior to the stomodaeum. Immediately posterior to this in- 

 vagination the three gnathal segments appear very much fused. 

 XII5- 



Fig. 76. Transverse section through the germ band of a Ctcnoccphalidcs felis 

 embryo showing the neural groove and coelomic sacs. The walls 

 of the sacs are thick and their lumina very small. This stage corre- 

 sponds to that shown in figure 77. X 400. 



Fig. 77. Portion of a parasagittal section through the germ band of a Cteno^ 

 ccphalides felis embryo showing the segmental arrangement of the 

 coelomic sacs. X 400. 



Fig. 78. Transverse section through the germ band of a Ctcnoccphalidcs felis 

 embryo showing how the neural groove is formed by the production 

 of paired longitudinal thickenings, one such thickening on each side 

 of it. The definitive body cavity or haemocoel, formed by the fusion 

 of the epineural sinus and the ruptured coelomic sacs, is also 

 shown. X 400. 



