REJUVENESCENCE IN NATURE. 15 



compared with what has been called, in the material 

 sphere, the specific formative impulse, or typical force. 

 Instinct is the continuation of the formative impulse in 

 a higher sphere, as is particularly clearly manifest in the 

 phenomena of the constructive impulse, in the formation of 

 envelopes and clothing (Serpula, Phyganea, Psyche), nests 

 and dwellings, as a kind of ulterior and more external 

 material organisation. The specific formative impulse, 

 however, is not an outwardly derived direction of the 

 activity, but one inwardly contained, acting, from internal 

 causes, as inner determination and force. This is shown 

 by the fact, that under like external conditions of exist- 

 ence, the organism shapes itself in a peculiar, specific, 

 nay even individual way, in each creature, whence the 

 multiformity of the picture which every mingled wood, 

 every meadow, every field, displays to us. Hence in the 

 grove we see the woodruff and the herb Paris, later in the 

 summer the willow-herb and the fox-glove, on the rock 

 the oak-fern, the dragon's-mouth, and the stone-crop, 

 side by side ; they take up the same nourishment, and 

 form their structures out of the same elements. What 

 maintains them in the distinctness ? It is the same force 

 that enables different animals to elaborate the same food 

 for such constantly varying bodily development, and, on 

 the other hand, prevents a considerable change of food 

 from effacing the specific type. This internally given 

 force of life is pre-eminently expressed in youth, while in 

 later age the formative forces are more and more fettered 

 to the products of their own activity, and work only in 

 a narrower circle, till at length their activity, every- 

 where more hampered in its own products, becomes 

 extinguished. 



For the definition of Rejuvenescence, we draw from 

 the foregoing considerations, the conclusion, that the 

 renouncement of forms already attained, and the retro- 

 gression to new rudiments, with which Rejuvenescence 

 begins, only mark the external side of the process, while 

 its inner and essential side is rather an inward gathering- 



