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Or let us suppose that certain other germ-cells in that 

 larva were to combine and coalesce to form a stomach, and 

 to push out prehensile arms around its mouth, pressing the 

 retained germ-cells into the substance of the thickened in- 

 tegument, or aggregating them near the base of the stomach : 

 if any of such germ-cells were to set on foot the process of 

 forming a germ-mass, it might protrude outwards, as in 

 the Hydra, and the embryo might include the stretched 

 portion of integument of the parent in the progress of its 

 development. 



But this development by gemmation would differ from 

 that ab ovo only in accessory and non-essential particulars ; 

 the nature of the essential spermatic force would be the 

 same. 



Such is the explanation which I have to offer of the 

 phenomena which meet us at the outset of our inquiries 

 into the generation of animals, and which I have grouped 

 together under the term c Parthenogenesis/ These phae- 

 nomena have hitherto remained the most obscure and seem- 

 ingly anomalous in the chapter of Comparative Physiology 

 relating to Generation; but, with this understanding of 

 their nature, they appear to me to enter into the ordinary 

 laws of the function, and to be disguised only by accessory 

 and non-essential modifications. Had I indeed, in the place 

 of such explanation, deduced from observation of the first 

 steps in development, salved these phenomena by the pro- 

 position " that they took place agreeably with the law of 

 alternate generation ;" " by the vital powers and by means 

 of the bodies" of the producing individuals; and had I 

 applied to the cercarial larva of the Distomata, to the po- 

 lypoid larva of the Medusae, and to the apterous larva of 

 the Aphides, the metaphorical phrase of f wet-nurses ' 

 and ' nursing-generations/ I should have succeeded in 

 concealing my own ignorance of the organic conditions 

 essential to these remarkable reproductive processes, in the 



