EMBRYOLOGY 



145 



mented elsewhere : the apertures in question are called micro- 

 pyles. They are sometimes protected by a micropyle apparatus, 

 consisting of raised processes, or porches : these are developed 

 to an extraordinary extent in some eggs, especially in those of 



B 



Fig. 78.— Eggs of lu- 

 sects : A, blowfly 

 (after Henking) ; B, 

 butterfly, Theda 



(after Scudder) ; C, 

 Hemipteron (Redu- 

 viid). 



Hemiptera-Heteroptera (see Fig. 78, C). Some of these peculiar 

 structures have been described and figured by Leuckart.^ The 

 purpose they serve is quite obscure. 



Formation of Embryo. 



The mature, but unfertilised, egg is filled with matter that 

 should ultimately become the future individual, and in the 

 process of attaining this end is the seat of a most remarkable 

 series of changes, which in some Insects are passed through with 

 extreme rapidity. The egg-contents consist of a comparatively 

 structureless matrix of a protoplasmic nature and of yolk, both 

 of which are distributed throughout the egg in an approximately 

 even manner. The yolk, however, is by no means of a simple 

 nature, but consists, even in a single egg, of two or three kinds 

 of spherular or granular constituents ; and these vary much in their 

 appearance and arrangement in the early stages of the develop- 

 ment of an egg, the yolk of the same egg being either of a homo- 

 geneously granular nature, or consisting of granules and larger 

 masses, as well as of particles of fatty matter ; these latter when 

 seen through the microscope looking sometimes like shining, 

 nearly colourless, globules. The nature of the matrix — which term 

 we may apply to both the protoplasm and yolk as distinguished 

 ' Mailer's Arch. Anat. Phys. 1855, p. 90. 

 VOL. V L 



