12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.98 



same paper, he fails to mention the presence of such bodies in this 

 species. Blochmann (1884, 1886, 1887a) studied these small cor- 

 puscles in the eggs of a number of insects and concluded that they 

 play an important part in embryonic development. Because he ob- 

 served their multiplication by transverse fission, he concluded them to 

 be bacterial organisms. Mercier (1906) substantiated Blochmann's 

 supposition by successfully culturing them in artificial media. Owing 

 to the great variability of the number of these bodies in flea eggs, it 

 seems improbable that they are of importance in the embryonic devel- 

 opment of these insects. No attempt was made to culture these 

 structures. 



MATURATION 



In unfertilized flea eggs, the position of the female pronucleus is 

 somewhat variable, being dependent upon the maturation processes. 

 Some of the preparations of newly deposited eggs show that they 

 contain only two nuclei and that these are lying close together in the 

 margin of the anterior polar plasm. Such a preparation apparently 

 represents a stage immediately following the first maturation division, 

 one of the two nuclei representing the first polar body and the other 

 the secondary oocyte. Sections from other newly laid eggs show that 

 the second maturation division has already taken place, as two polar 

 body nuclei may be seen lying in the periplasm, while a third or ootid 

 nucleus lies toward the interior of the egg. The polar body nuclei of 

 fleas, like those of other insect forms, are never extruded from the egg 

 but remain within the anterior periplasm until they disintegrate. The 

 first polar body appears to remain undivided. Following the second 

 maturation division the ootid nucleus migrates toward the center of 

 the egg. Oviogenesis, or the differentiation of the ootid nucleus into 

 the female gametic nucleus, takes place during this migration. This 

 maturing process prepares the female nucleus for syngamy with the 

 male gametic nucleus. 



SYNGAMY 



Figure 12 (pi. 1) shows a longitudinal section through the anterior 

 half of a cat flea egg in a stage just prior to syngamy. Only four 

 nuclei are evident in the entire egg and three of them are present in 

 this section. These are the female gametic nucleus, the male gametic 

 nucleus, and one of the polar body nuclei. The second polar body 

 lies at a different level and appears in another section. The large 

 number of micropylar openings occurring in flea eggs is suggestive of 



