136 ESSAY ON CLASSIFICATION. 



progeny which runs with never-varying regularity through 

 the same course, there are others which multiply in 

 various ways, by division and by budding, 1 or by a 

 strange succession of generations, differing one from the 

 other, and not returning in a direct course to their 

 typical cycle. 



The facts which have led to the knowledge of the 

 phenomenon now generally known under the name of 

 alternate generation were first observed by Chamisso and 

 Sars, and afterwards presented in a methodical connection 

 by Steenstrup, in his famous pamphlet on that subject. 2 

 As a brief account of the facts may be found in almost 

 every text-book of Physiology, I need not repeat them 

 here, but only refer to the original investigations, in 

 which all the details known upon this subject may be 

 found. 3 These facts show, in the first place, with regard 

 to Hydroid Medusae, that individuals born from eggs 

 may be entirely different from those which produced the 

 eggs, and may end their life without ever undergoing 

 themselves such changes as would transform them into in- 



1 Much information useful to the tion of Procreating Individuals from 



zoologist, may be gathered from a single Ovum ; London, 1849, Svo. 



BRAUN'S paper upon the Budding of On Metamorphosis and Metagene- 



Plants, q. a., p. 24, note 3. The pro- sis, Ann. and Mag. Nat. Hist., 2d ser. 



cess of multiplication by budding or vol. 8, 1857, p. 59. PROSCH, (V.,) 



by division, and that of sexual repro- On Parthenogenesis og Generations- 



duction, are too often confounded by vexel et Bidrag til Generationslseren ; 



zoologists, and this confusion has al- Kiobenhavn, 1851. LEUCKART, (R.,) 



ready led to serious misconstructions Ueber Metamorphose, ungeschlecht- 



of well known facts. liche Vermehrung, Generationswech- 



3 STEENSTRUP, J.,) Ueber den Ge- sel, Zeitsch. f. wiss. Zool., vol. 3, 1851. 



ncrationswechsel, q. a., p. 103, note 3. DANA, (J. D.,) On the Analogy be- 



3 See the works quoted above, p. tween the Mode of Reproduction in 



103, note 3, and p. 105, note 1, also Plants and the " Alternation of Gene- 



CARUS, (V.,) Zur nahern Kenntniss rations" observed in some Radiata, 



des Generationswechsels ; Leipzig, Amer. Journ. A. and Sc., 2d ser. vol. 



1849, 8vo. Einige Worte iiber Me- 10, p. 341. EIIRENBERO, (C. G.,) 



tamorphose und Generationswechsel, Ueber die Formeubestiindigkeit und 



Zeitsch. f. wiss. Zool., 1851, vol. 3, den Entwickelungskreis cler organ- 



p. 359. OWEN, (R.,) On Partheno- ischen Formeu,Mouatsber. dcr Akad. ; 



genesis, or the Successive Produc- Berlin, 1852, 8vo. 



