Royal Institution. 65 



The wingless larval Aphides are not very locomotive ; they might 

 have been attached to one another by continuity of integument, and 

 each have been fixed to suck the juices from the part of the plant 

 where it was brought forth. The stem of the rose might have been 

 incrusted with a chain of such connected larvae as we see the stem 

 of a fucus incrusted with a chain of connected polypes, and only the 

 last developed winged males and oviparous females might have been 

 set free. The connecting medium might even have permitted a 

 common current of nutriment contributed to by each individual to 

 circulate through the whole compound body. But how little of 

 anything essential to the animal would be affected by cutting through 

 this hypothetical connecting and vascular integument, and setting 

 each individual free! If we perform this operation on the compound 

 zoophyte, the detached polype may live and continue its gemmiparous 

 reproduction. This is more certainly and constantly the result in 

 detaching one of the monadiform individuals which assists in com- 

 posing the seeming individual whole called ' Volvox globator ' ; and 

 so likewise with the leaf-bud. And this liberation Nature has actually 

 performed for us in the case of the iVphis, and she thereby plainly 

 teaches us the true value or signification in morphology of the con- 

 necting links that remain to attach together the different gemmi- 

 parous 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-gene- 

 rations preceding the flower. 



It would have been easy, if time permitted, to multiply the illus- 

 trations of the essential condition of these phaenomena. That 

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

 fertilized 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 

 constituted the individual containing them. 



How the retained pollen-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 



Ann. $ Mag. N. Hist. Ser. 2. Vol. viii. 5 



