212 SUMMARY OF CONCLUSIONS. 



IX. 



SUMMARY OF CONCLUSIONS. 



§ 1. Having discussed, in tlie preceding chapters, the distinc- 

 tions observable among cases of alternation of Generations, 

 and the phenomena which may be thought in some way to 

 represent them in the higher species, and having stated 

 the general results of later observations in reference to the 

 relations of ova and gemmae, it may be advisable to give 

 here a short summary of the conclusions arrived at, as 

 affording that explanation of the facts which appears, on 

 the whole, the most probable, if not in all cases positively 

 ascertained. They may be stated as follows : — 



I. — The function of reproduction is performed in two 

 ways — by gemmation (monogenesis), and by sexual union 

 (digenesis.) In the former, a portion of the body of the 

 parent becomes the seat of a certain independent vitality, 

 and may eventually be detached and transformed, by a pro- 

 cess of self-development, into a distinct organism (zooid or 

 phytoid). In the latter, the germ of the new being is the 

 result of fecundation — that is, of the fusion of two highly 

 organized portions (speimatic and germinal) of the same or 

 of kindred organisms, which stand in the relation of 

 parents. 



II. — There is reason to believe that the same portion of 

 the parenchyma of the parent may be organised in either 

 of these ways ; but, in general, in proportion as it is engaged 

 in the one course it is disabled from the other ; thouo:h a 

 few cases are known in which a part already organized as 

 an ovum may yet be developed as a gemma, that is, with- 

 out impregnation. 



