I 



384 



PROVISIONAL HYPOTHESIS. 



Chap. XXVII, 





zoon of an insect finds its way into the minute micropyle of the 

 egg, or as when the antherozoids of 



certain algae 



s wj m 



the aid of their cilice to the female plant, and force themselves 

 into a minute orifice. In these latter cases, however, we must 

 believe that the male element has acquired its powers, on the 

 same principle with the larvae of animals, namely by successive 

 modifications developed at corresponding periods of life : we 

 can hardly avoid in these cases looking at the male element 

 as a sort of premature larva, which unites, or, like one of the 

 lower algae, conjugates, with the female element. What deter- 



of the aremmules within the sexual 



mines the 



aggregation 



organs we do not in the least know ; nor do we know why buds 

 are formed in certain definite places, leading to the symmetrical 

 growth of trees and corals, nor why adventitious buds may be 

 formed almost anywhere, even on a petal, and frequently upon 



healed wounds. 39 As soon as the gemmules have aggregated 



during 



a 



themselves, development apparently commences, but in the case 

 of buds is often afterwards suspended, and in the case of the 

 sexual elements soon ceases, unless the elements of the opposite 

 sexes combine ; even after this has occurred, the fertilised germ, 

 as with seeds buried in the ground, may remain 

 lengthened period in a dormant state. 



The antagonism which has long been observed, 40 though ex- 

 ceptions occur, 41 between active growth and the power of sexual 

 reproduction — between the repair of injuries and gemmation 

 and with plants, between rapid increase by buds, rhizomes, 



the 



&c, and the production of seed, is partly explained 

 gemmules not existing in sufficient numbers for both processes. 



39 See Rev. J. M. Berkeley, in ' Gard. 

 Chron.,' April 28th, 1866, on a bud 



Hist.,' 3rd series, 18G6, p. J 57), are 

 capable of reproduction. Ernst Hackel 

 developed on the petal of the Clarkia . has recently (' Monatsbericht Aka<-. 

 See also H. Schacht, ' Lehrbuch der Wiss. Berlin,' Feb. 2nd, 1865) ob- 

 Anat.,' &c, 1859, Theile ii. s. 12, on served the surprising case of a medusa, 

 adventitious buds. with its reproductive organs active, 



40 Mr. Herbert Spencer (' Principles which produces by budding a widely 

 of Biology,' vol. ii. p. 430) has fully different form of medusa; and this 



latter also has the power of sexual re- 

 production. Krohn has shown ('Annals, 



discussed the 



growth and reproduction. 



antagonism between 



41 The male salmon is known to breed and Mag. of Nat. Hist.,' 3rd series, vol. 

 at a very early age. The Triton and xix. 1862, p. 6) that certain other 

 Siredon, whilst retaining their larval medusse, whilst sexually mature, pro- 

 branchiae, according to Filippi and pagate by gemmse. 

 Dumeril (' Annals and Mag. of Nat. 







