Professor Owen on Metamorphosis and Metagenesis. 277 



value or signification in morphology of the connecting links 

 that remain to attach together the different gemmiparous 

 individuals of the volvox, the zoophyte, and the plant. 



The analogy between the procreating larvae of the Aphis, 

 the Medusa^ and the Coralline is so true and so close, that if 

 the larval Aphis be a distinct individual and not a part, so 

 must be the strobila, the planula, and the gemmiparous leaf: 

 if the succession of larval Aphides be truly described, as a 

 succession of generations, so must that succession of planula, 

 polype and strobila which leads to the oviparous Medusa : 

 and that succession of planulae and nutritive polypes which 

 precede the detachment of the free procreative medusoid 

 polypes in the Coryne ; and the like with the plant genera- 

 tions preceding the flower. 



It would have been easy, if time permitted, to multiply 

 the illustrations of the essential condition of these phenomena. 

 That condition is, the retention of certain of the progeny of 

 the primary fertilised germ-cell, or in other words, of the 

 germ-mass, unchanged in the body of the first individual 

 developed from that germ-mass, with so much of the pollen 

 force inherited by the retained germ-cells from the parent- 

 cell or germ-vesicle as suffices to set on foot and maintain 

 the same series of formative actions as those which consti- 

 tuted the individual containing them. 



How the retained pollen-force or seminal-force operates in 

 the formation of a new germ-mass from a secondary, tertiary, 

 or quaternary derivative germ-cell, the Lecturer did not 

 profess to explain ; neither was it known how it operates in 

 developing the primary germ-mass. 



The botanist and physiologist congratulates himself with 

 justice when he has been able to pass from cause to cause, 

 until he arrives at the union of the pollen-filament with the 

 ovule as the essential condition of development — a cause 

 ready to operate when necessary circumstances concur, and 

 without which those circumstances would have no effect. 



The chief aim of the present discourse was to point out 

 the circumstances which bring about the presence of the 

 same essential cause in the cases of the development of the 

 successive generations completing the metagenetic cycle of 



