Chap. XXVII. OF PANGENESIS. 379 



wonder would be that parthenogenesis did not occur much 

 oftener than it does. On any ordinary theory of reproduction 

 the formation of graft-hybrids, and the action of the male 

 element on the tissues of the mother-plant, as well as on the 

 future progeny of female animals, are great anomalies ; but 

 they are intelligible on our hypothesis. The reproductive 

 organs do not actually create the sexual elements ; they 

 merely determine the aggregation and perhaps the multipli- 

 cation of the gemmules in a special manner. These organs, 

 however, together with their accessory parts, have high 

 functions to perform. They adapt one or both elements for 

 independent temporary existence, and for mutual union. The 

 stigmatic secretion acts on the pollen of a plant of the same 

 species in a wholly different manner to what it does on 

 the pollen of one belonging to a distinct genus or family. 

 The spermatophores of the Cephalopoda are wonderfully 

 complex structures, which were formerly mistaken for para- 

 sitic worms ; and the spermatozoa of some animals possess 

 attributes which, if observed in an independent, animal, would 

 be put down to instinct guided by sense-organs, — as when 

 the spermatozoa of an insect find their way into the minute 

 micropyle of the egg. 



The antagonism which has long been observed, 55 with 

 certain exceptions, between growth and the power of sexual 

 reproduction 56 — between the repair of injuries and gemma- 

 tion — and with plants, between rapid increase by buds, 

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

 by the gemmules not existing in sufficient numbers for these 

 processes to be carried on simultaneously. 



53 Mr. Herbert Spencer (' Princi- of a medusa, with its reproductive 



pies of Biology,' vol. ii. p. 430) has organs active, which produces by 



fully discussed this antagonism. budding a widely different form of 



56 The male salmon is known to medusa ; and this latter also has the 



breed at a very early age. The power of sexual reproduction. Krohn 



Triton and Siredon, whilst retaining has shown (' Annals and Mag. of 



their larval branchia?, according to Nat. Hist.,' 3rd series, vol. xix., 1862, 



Filippi and Dumeril ('Annals and p. 6) that certain other medusae, 



Mag. of Nat. Hist.,' 3rd series, 1866, whilst sexually mature, propagate 



p. 157), are capable of reproduction. by gemmae. See, also, Kolliker, 



Ernst Haeckel has recently (' Monats- ' Morphologie und Entwickelungsge- 



bericht Akad. Wiss. Berlin,' Feb. 2nd, schichte des Pennatulidenstammes, 



186j) observed the surprising case 1872, p. 12. 



