326 Insects' Eggs. 



served, at some time, while the egg was yet a part of the 

 ovarium ovum, as avascular coat, and being no longer required, 

 has become consolidated to form a part of the dense membra- 

 naceous covering. 



It is in these several layers of the outer membrane that the 

 micropyle apparatus is situated, and it should be noted that 

 Meissner has described several varieties of the micropyle in the 

 ova of insects belonging to the following genera, viz., muscce, 

 tipula, pulex, lampyris, elater, ieleophorus , aclela, pyralida, tor- 

 trix, euprepia, liparis, pieris, panorpa, and in more than one 

 species of several of these genera. The same author also observed 

 and described in Musca vomitoria, a number of spermatic fila- 

 ments entangled in the nricropjde. Leuckart's observations, 

 which are apparently more complete than those of Meissner, differ 

 from his in some particulars; they extend over several hundreds 

 of different kinds of insects' eggs, and he asserts that he suc- 

 ceeded in detecting the existence of the micropyle in not 

 less than 200 : he also gives detailed observations on this 

 apparatus, and the structure of the membranes. I wil- 

 lingly admit that such an extended series of observations fully 

 entitles this author to great respect ; and when we consider 

 the minuteness of the eggs, and the difficulty of obtaining speci- 

 mens in a suitable condition for investigations of the kind, we 

 may appreciate the importance of the work, and the amount of 

 labour required to bring such an investigation to a satisfactory 

 conclusion. Leuckart positively asserts that, " in all instances 

 in which the ova were ripe and favourable for examination, he 

 was enabled to assure himself of the presence of the micropyle." 

 This supposed opening will be readily recognised in many of 

 the drawings accompanying this paper, forming, as it does, a 

 prominent spot at the pole of the egg, or in the middle of 

 the circular radiants in the lid. 



The outer surface of the eo:s: shell of Coccus Persicce is 



o o 



covered by a series of minute rings, the ends of which some- 

 what overlap. These rings are believed by Sir John Lubbock 

 to be identical in their character with the whitish substance 

 which exudes through pores on the underside of the body; and 

 it is more than probable that these layers of rings, and their 

 arrangement, account for the beautiful prismatic hues which 

 the egg presents under the microscope, when viewed as opaque 

 objects. This substance, it appears, ultimately becomes a part 

 of the intimate structure of the egg membranes. With regard 

 to the greenish colour of the eggs of Phri/ganea, the same 

 observer states " that it is due to the yolk-globules 

 themselves.* In Coccus this is not the case, the yolk-globules 

 are slightly yellow, and the green hue of the egg is owing to 



* Tliil. Trans. 1868, v. 3 11. 



