IO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 98 



poles ; the anterior apparatus in this species was found to possess 30 

 to 40 such openings, whereas the posterior one gave counts of from 

 15 to 25. In all three species studied, the openings at each pole were 

 found to tend toward a spiral arrangement. 



In Hystrichopsylla dippiei there may be a number of volcanolike 

 raised processes arranged irregularly around the margin of the micro- 

 pylar area (pi. 1, fig. 2). Their general appearance suggests the so- 

 called micropyles of Phyrrhocoris apterus illustrated by Packard 

 (1898, fig. 501), but longitudinal sections through them have failed 

 to demonstrate for certain that the minute canals which pass inward 

 from their craters perforate the chorion. Therefore, their function as 

 supplementary micropyles is doubtful. The eggs of Nosopsyllus 

 fasciatus and Ctenocephalidcs felis appear to lack these peculiar 

 structures. 



Balbiani (1875) was °f the opinion that in cat flea eggs only the 

 anterior group of micropylar openings served as passageways for the 

 entrance of spermatozoa, since he found what he interpreted as 

 spermatic filaments caught only in the anterior openings. None of the 

 preparations made during the present study show any structures lodged 

 in the openings of either pole which may be interpreted with any 

 degree of certainty as spermatic tail pieces. Furthermore, longitudinal 

 sections of the eggs of all three species demonstrate clearly that the 

 lumina of the pores of both the anterior and the posterior micropylar 

 apparatuses pass through the chorion. It is probable, therefore, that 

 in the case of flea eggs the openings of both the anterior and pos- 

 terior micropylar areas serve as passageways for the entrance of 

 spermatozoa. 



The difference in the number of micropylar pores present at the 

 poles is the only external indication of anterior-posterior differentia- 

 tion in flea eggs. The identification of the poles was made by opening 

 eggs in which the embryos had developed sufficiently to permit positive 

 recognition of the cephalic and caudal ends. This identification made 

 it possible to test the Law of Hallez (1886) as applied to flea eggs. 

 Eggs for this purpose were dissected from the oviduct, and invariably 

 their anterior poles were directed toward the head of the mother. Be- 

 cause flea eggs possess no dorsoventral differentiation until develop- 

 ment is well advanced, no attempt was made to test the Law of Hallez 

 in respect to this second axis. 



Some authors, such as Huettner (1923), describe a third protective 

 membrane for insect eggs. This they term the plasma membrane. It 

 is described as an extremely thin investment adhering closely to the 



