60-1 THE MICROSCOPE. 



tions made on the silkworm, we have not been able to 

 satisfy ourselves of the correctness of these particulars : 

 in every case, indeed, the young worm makes its way out 

 from a point generally below this spot. Leuckart, how- 

 ever, expresses his belief in this micropyle, and says, " It 

 becomes at a later period converted into a funnel, which is 

 connected directly with the mouth of the embryo, and 

 serves to convey nourishment from without to it." We, 

 on the contrary, look upon it as an involuted portion of 

 membrane, indicating the spot where the formative pro- 

 cess of the outer membrane terminated, or where at a still 

 earlier stage, and while the ova was yet in the ova-sac, the 

 spermatozoa passed in to fecundate the yolk mass. 



The germinal vesicle is very large and well marked, 

 while the egg is yet in the ova-sac of the insect. By pre- 

 paring sections, after Dr. Hallifax's method, 1 we find that 

 the germinal vesicle in the bee's egg is not situated imme- 

 diately near or even below the so-called micropyle, but 

 rather more to the side of the egg ; just in the position 

 which the head of the embryo is subsequently found to 

 occupy when it arrives at maturity. 



The egg membrane, or envelope, of all the Lepidop- 

 tera, is composed of three separate and distinct layers : 

 an external slightly raised coat, tough and hard in its 

 character, a middle one of united cells, and a fine trans- 

 parent vitelline lining membrane, perfectly smooth and 

 homogenous in structure, imparting solidity, and giving a 

 fine iridescent hue to the surface, such as most of us admire 

 in old glass exhumed from the ruins of Pompeii. The 

 germinal vesicle is of a proportionately large size for the 

 egg, and its macula is at first single, then multiple. In 

 the silk-worm's egg the outer membrane is comprised of 

 an inner reticulated membrane of non- nucleated cells, and 

 in the outer layer the cells are arranged in an irregular 

 circular form, also non-nucleated, with minute interstitial 

 setae or hairs projecting outward. 



The outer surface of the egg-shell of Coccus Persicce is 



(1) Dr. Hallifax adopts the method of killing the insect with chloroform : he 

 then immerses it in a bath of hot wax, in which it is allowed to remain until the 

 wax becomes cold and hard ; now with a sharp knife a section is easily made in 

 the required direction without in the least disturbing any of the fragile parts, 

 or internal organs. 



