192 THE entomologist's record. 



Tl^c Life-jiistopy of a Lepidopterous Insect, 



Comprising some account of its Morphology and Physiology. 



By J. W. TUTT, F.E.S. 



{Continued from page 169). 



Chap. IV.* '. 

 EMBKYOLOGY. 



1. — General remarks on the study of embryology. — Embryology 

 concerns itself with the cycle of changes that take place in the fertilized 

 ovum, and that have as their result the production of an individual 

 resembling its parents. Biologists are agreed as to the supreme im- 

 portance of the subject, for many of the profounder mysteries of living 

 creatures can only be interpreted by its aid. More and more, therefore, 

 of late years has its study engaged the attention of scientific men, and 

 entomology, like other branches of natviral history, has received illumi- 

 nation from their labours. It is now well known that all animals 

 during their embryonic life undergo a series of remarkable changes 

 both in form and structure. Sir John Lubbock tells us that ChVoeon 

 (an Ephemerid insect) moults some twenty times before reaching its 

 final stage of development, whilst every entomologist has watched the 

 more or less sharply defined metamorphoses that other insects undergo. 

 I may remark that for the present I give the word Embryology a wider 

 meaning than, strictly speaking, is warranted, and include all the con- 

 ditions through which the young pass before reaching actual maturity 

 as simply extensions of the embryological condition. How great are 

 the changes which various animals and plants undergo during develop- 

 ment, we all know. In the case of a fern there is first the spore ; this 

 gives rise to the prothallium, which in its turn produces antheridia and 

 archegonia ; the latter undergo fertilization, and it is not till the con- 

 sequent development of the germ-cell is comj^leted that the cycle of 

 change is ended by the reproduction of a fern. Again, we may take 

 a branching coralline ; this gives off a vast number of huge, free-floating 

 jelly-fishes, which in their turn produce cells from which free-swim- 

 ming ciliated animalcules are developed ; these after a time become 

 attached to rocks and reproduce the coralline. Or, taking an example 

 from an insect, the larva of a Dipteron (Cecidomyia) produces asexually 

 other larvae ; these pupate, and from the pupae male and female 

 imagines emerge ; pairing ensues, and eggs are laid from which larvae 

 hatch, and the cycle begins again. In some cases the greater part of 

 embryonic life is got through before the embryo has a separate existence 

 from the parent, in others after it has such separate existence ; so that 

 although the embryonic condition is often spoken of as if it were 

 limited to the development of the young within the egg, the term 

 really has a much wider application. 



2, — On the similarity between the earliest embkyonk; stages 

 OF WIDELY DIFFERING CREATURES.— In their earliest embryonic stages 

 the various divisions of the largest classes of the Animal Kingdom 

 present a remarkable similarity as regards their structural features. 



* ChaiJ. III. on Parthenogenesis uill follow this chapter. The material for 

 it is not yet complete. 



