ClIAP. I. 



METAMORPHOSES OF ANIMALS. 



G7 



tlie metamorphoses of Insects became very early the subject of most remarkable 

 observations,' but so little was it then known that all animals inidergo great changes 

 from the first to the last stages of their growth, that mctamorphosLs was considered 

 a distinguishing character of Insects. The diflerences between Insects, in that 

 resi^ect, are however already so great, that a distinction was introduced between 

 those which undergo a complete metamorphosis, that is to say, which appear in 

 three successive different forms, as larvte, pupte, and perfect insects, and those with 

 an incomplete metamor2)hosis, or whose larvae differ httle from the perfect insect. 

 The range of these changes is yet so limited in some insects, that it is not only 

 not greater, but is even much smaller than in many representatives of other classes. 

 We may, therefore, well apply the term metamorjihosis to designate all the changes 

 which animals undergo, in direct and immediate succession,^ during their growth, 

 whether these changes are great or small, provided they are correctly qualified for 

 each type. 



The study of embr3'ology, at first limited to the investigation of the changes 

 which the chicken undergoes in the egg, has gradually extended to eveiy tj^pe 

 of the animal kingdom; and so diligent and thorough has been the study, that 

 the first author who ventured upon an extensive illustration of the whole field, 

 C. E. von Baer, has already presented the subject in such a clear manner, and 

 drawn general conclusions so accurate and so comprehensive, that all subsequent 

 researches in this department of our science, may be considei'ed only as a further 

 development of the facts first noticed by him and of the results he has already 

 deduced from them.^ It was he who laid the foundation for the most extensive 



* SwAMMERDAM, (.J.,) Biblia Naturrc, sive Ilis- 

 toria Inseclonim, etc., Lugdiini-Hatavorum, 1737-38, 

 3 vols. fol. fig. — Reaumur, (R. Ant. de,) Memoires 

 pour servir a I'Hisloire des Insectes, Paris, 1734—42, 



6 vol. 4tO. fig. ROESEL VON' ROSENIIOF, (A. J.,) 



Inseptenbflustigiing<.'n, Niirnberg, 1746-61, 4 vols. 

 4to. fig. 



' I say purposely, " in direct and immediate suc- 

 cession," as the plienomona of alternate generation 

 are not included in inetuniorphosis, and consist <'luetly 

 in tlic production of new germs, which have their 

 own metamorphosis ; while metamorphosis proper 

 relates only to the successive changes of one and 

 the same germ. 



* Without referring to the works of older writers, 

 such as DeGraaf, Malpighi, Ilaller, Wolf, Jleckel, 

 Tiedemann, etc., which are all cinnnerated with nianv 



others in Bisciioff's article '• Entwickelung>ges- 

 chichte," in Wacner's Ilandwiirterbuch der Pliysio- 

 logie, vol. 1, ]). 860, I shall mention hereafter, chiefly 

 those published since, under the influence of Diillin- 

 ger, this branch of science has assumed a new char- 

 acter: — Baek, (C. K. v.,) Ueber Entwickelungs- 

 geschichte der Thiere, Kiinigsberg, 1828-37, 2 vols. 

 4to. fig. The most important Avork yet published. 

 The preface is a mod(d of candor and trutlifnlness, 

 •and sets the merits of TXillinger in a true and beanti- 

 fnl light. As text-books, I would quote, Bihd veil. 

 (C. F.,) Die Physiologic als Erfahrungswissenscluift, 

 Leipzig, 1829-40, C vols. 8vo. ; French, Paris, 

 1837-41, 9 vols. 8vo.— MuLLER, (.J.,) Ilandbuch der 

 Physiologic des Menschen, t'oblenz, 1843, 2 vols. Bvo. 

 4th edit. ; Engl, by W. Baly, London, 1837, 8vo. 

 — Wagner, (H.,) Leiirbuch der Physiologic, Lcip- 



