PLAN AND PURPOSE IN NATURE. 201 



early period of its life-history processes called karyokinesis, 

 segmentation, gastrulation, formation of blastoderm with 

 primitive entoderm and ectoderm. Then further differentia- 

 tion of its cells into organ after organ takes place. The 

 ovum becomes attached to the protecting and nourishing 

 maternal walls. Expansion of these and enlargement of 

 vessels, which are eventually massed togetlier for the 

 placenta, takes place. At this period the growing ovum 

 requires a change in its environment, though it must still be 

 attached to the maternal surface. A group of ^'essels inter- 

 twined with fibrous tissue becomes the placenta, a cord con- 

 taining an artery and vein supplies a direct communication 

 of its blood with that of the mother, by which means oxy- 

 genation of the foetal blood takes place. The ovum is 

 delicate and requires protection. Fluid forms round it. 

 The maternal parts, its temporary habitation, enlarge ; 

 muscular tissue, perhaps dormant for many years before, 

 becomes enormously enlarged for future use. In due time 

 the need for all these elaborate contrivances comes to an 

 end. Means are ingeniously provided for the extrusion of 

 the ovum when mature, and its other life when born. Such 

 a remarkable process as this, preordained from the moment of 

 fertilization, in which, strange to say, Huxley could almost, 

 but not quite, see "the Hidden Artist" at work, witli the 

 eyes of his faith, may be repeated in identical fashion many 

 times in the life of one animal. But these and many other 

 changes in the ovum which have not been referred to, and 

 the discovery of which constitutes some of the most brilliant 

 and exact results of biological science, could not proceed 

 beyond a few halting steps were it not for the preordained 

 conditions for its coming life, meeting it at every stage of its 

 development. Indeed a most apposite comment upon the 

 cogency of the argument here maintained is supplied by an 

 experience, happily rare, known to medical men as ectopic 

 gestation. Here the ovum is diverted from its suited and 

 preparing home : it develops up to a certain lamentable 

 degree in its abnormal position, an exile from its home, until 

 a fatal result to mother and ovum is seldom averted, and then 

 only by the exhibition of surgical skill brilliant among many 

 brilliant triumphs ; Avhicli is a sad and apt comment upon the 

 interruption of Design on the one hand, and on the other upon 

 the power of mind, albeit a human mind. 

 12 The length and simplicity of this illustration may be 

 pardoned for the sake of the light thrown by it on one aspect 



