REJUVENESCENCE IN NATURE. 3 



annually, throwing off the old one ; the crab changes even 

 his old stomach for a young one, every year. The 

 cotyledons, and even the radical leaves, as they are termed, 

 have already yielded to age in the (Enothera, the rape, 

 and many other plants, at a time when the flowers still 

 remain in a young condition of buds, and, on the other 

 hand, the floral envelopes have perished when the fruit 

 is only in the commencement of its process of matura- 

 tion. In the pupa of the grasshopper, all the external 

 organs are fully developed, at a time when the wings are 

 just beginning to be formed. So may Man be a mere 

 child in mental development, when already old in bodily 

 respects. We see youth and age, therefore, presenting 

 themselves alternately in one and the same course of 

 development ; we see youth break forth in age, and enter 

 into the midst of the process, for the purpose of com- 

 pleting or metamorphosing the structures. This is the 

 phenomenon of Rejuvenescence (Verjiingung), which is 

 repeated in infinitely varied ways in all domains of life, 

 but nowhere asserted more distinctly and more accessibly 

 to investigation, than in the Vegetable kingdom. With- 

 out Rejuvenescence there can be no progressive develop- 

 ment ; only the lifeless creation, or rather, that dying in 

 the moment of production, the mineral, is devoid of the 

 power of Rejuvenescence ; whence it is also deprived of 

 development and propagation. 



Rejuvenescence appears, in the first place, as a return 

 to an earlier condition of life, whereby is obtained a point 

 of departure for renewed progress; or, in the extreme 

 case, as a retrogression to the commencement of the 

 entire course of development, to attain the aim in a repe- 

 tition of the development. The former we see in the 

 Rejuvenescences of the individual within the course of its 

 individual development, the latter in the Rejuvenescence 

 of the species through the succession of individuals. The 

 retrogression just mentioned, introducing the Rejuve- 



in the foetus of the whale. According to Eschericht the foetus of Balcenop- 

 tera longim-ana has 102 teeth iu the upper, and 84 in the lower jaw. 



