THE LIFE-HISTORY OF A LEPIDOPTEROUS INSECT. 211 



accessories, and I do my work with two lenses, a 2^3 and i/s, which I 

 find sufficient for all practical purposes. Should anyone wish to go 

 more deeply into the subject, his requirements will teach him what he 

 must get in addition, but, for the simple observation of development in 

 the egg, this is sufficient. When we have placed a suitable egg under 

 the microscope, and watched the various changes which it undergoes, 

 we are compelled to admit that — 



•' There is a wondrous workshop here, 

 E'en in this dainty little pod, 

 Here that mj'sterious workman Life, 

 Builds matchless temples to his God." 



To get eggs for this purpose, take an ordinary glass tube and enclose 

 a few females of some common Tortrix moths. They will usually lay 

 eggs on the glass, and their egg-shells are so transparent, that the 

 changes may be most readily observed. The eggs of Pararge megaera, 

 Nemeobius lucina, and many others, are also good objects for this 

 purpose. 



7. — On killing eggs in which the embryo is developing for 

 FUTURE observation. — It is sometimes inconvenient to study the em- 

 bryological changes which go on in an egg under a microscope at the time 

 that they actually occur, and in Insect life (vol. i., p. 316) a very good 

 method is described, by which the eggs may be killed and preserved for 

 future observation, although it is one which requires a considerable 

 amount of care in manipulation. The eggs are obtained in the ordinary 

 course, and as soon as a batch is laid, the eggs are distributed in a 

 number of homceopathic phials, each about one inch high, with data, 

 etc., on the cork. At the end of the first day one phial is filled with 

 carbolic acid, another on the second day, and so on, until on the last 

 day a bottle is filled containing newly-hatched larvte. It is found that 

 the acid renders the eggs perfectly transparent, so that the embryo can 

 be observed in various stages of development. The recorder states that 

 he mounts in benzole balsam direct from the carbolic acid. Of coui'se 

 there are many insects whose eggs cannot be served in this way ; at 

 the same time there are hundreds of species whose eggs can be thus 

 manipulated. Mr. Woodvvorth describes another method of attainino- 

 this end: — "The method of preparation which seems to have given 

 the best results, is to kill by heating in water at 8U"C, which fixes the 

 tissues very well. Eggs must now be punctured with a sharp needle. 

 This is essential in order that the reagents used may j^enetrate. The 

 most satisfactory stains are Grenachar's borax carmine, and Czochar's 



cochineal. The latter is especially good. It is prepared as follows : 



Place 1 gramme each of cochineal and burnt alum in a mortar, and 

 reduce to a powder; add lOU cc. of distilled water, and boil until there 

 are but 60 cc, cool and filter ; a few drops of carbolic acid should be added 

 as a preservative. The hardness of the egg-shell makes the egg very 

 difficult to section, but if removed, it is so delicate as to be almost certain 

 to go to pieces during the further manipulation. The parafin metliod 

 of imbedding was employed, and the sections cut on the rockino- 

 microtome made by the Cambridge Instrument Co." 



8. — On the formation of the egg. — The evolution of every livino- 

 being from a single unicellular germ is an established fact of science. 

 The egg in insects is not quite the earliest condition of the creature 

 because the primitive ovule can be traced back to the ovuriole or even 

 to the primitive ovary before the ovariole is developed. 



