SUMMARY AND CONCLUSIONS 1.71 



Sometimes a degenerative transformation becomes 

 still more complete and wonderful ; riot only may 

 a larval stage or an adult stage be completely 

 suppressed, but a multicellular organism may even 

 lose its power of dying. It is known that the 

 simplest forms of life are practically immortal : 

 when a microbe like micrococcus divides nothing 

 dies, and throughout the whole series of successive 

 divisions the primitive life is preserved. On the 

 other hand, in the case of higher animals such as 

 man there are both mortal somatic cells and 

 reproductive cells which by means of conjugation 

 become practically immortal. The mortality of the 

 somatic cells is evidently an acquisition, an advant- 

 age fixed by natural selection ; but there exist 

 multicellular organisms evidently derived from 

 creatures which had acquired the division into 

 mortal somatic and immortal reproductive cells and 

 which have lost it since. All the cells of their 

 body are able to avoid death by conjugation. 

 This occurs in many conjugate algse like spirogyra 



this species do not actually reach the adult stage. According to 

 Boas writing on Neotenie in Gegenbaur's Festschrift, 1896, this 

 probably happens in the case of all the perennibranchiate urodeles. 

 Ranunculacece. On page 85 we showed that in Ranunculus 

 aquatilis there are produced first submerged leaves, and afterwards 

 floating lobed leaves, and that the flowers are produced in the 

 axils of the floating leaves. Some forms of the plant living in 

 deep water produce only lacinated leaves, in the axils of which by 

 a kind of psedogenesis the flowers are produced. In other species 

 (Ranunculus fluitans and R. divaricatus) the predogenesis has 

 become definitely established and no floating leaves are formed. 



