196 PROF. HUXLEY ON THE AGAMIC REPRODUCTION 



antennEe. It was only in November that the apterous females presented eggs in their 

 ovaries and oviducts, and for that effect, a considerable degree of cold was necessary*." 



lilorren describes the male, female, and agamic organs of reproduction, but less com- 

 pletely than Von Siebold, who, in 1839t, carefully investigated the Aphis Lonicerce, and 

 lirst demonstrated the existence of the spermatheca and coUeterial glands in the oviparous 

 females. Von Siebold distinguishes three forms of this species, two winged and one 

 apterous. The large winged Aphides were all viviparous ; the smaller, males. The 

 apterous forms were oviparous, and the progeny of the alate females. 



Steenstrup says of the ApjUides (Alternation of Generations, p. 108), " The propagation 

 of these creatiu-es through a series of generations has been ah'eady long known. In the 

 spring, for instance, a generation is produced from the ova, which grows and is metamor- 

 phosed, and without previous fertilization gives birth to a new generation, and this again 

 to a thii"d, and so on for ten or twelve weeks ; so that in certain species even as many as 

 nine such preliixdnary generations will have been observed; but at last there always 

 occurs a generation consisting of males and females, the former ofiohkh after their meta- 

 morphosis are usually winged ; fertilization and the depositing of eggs take place, and 

 the Ions: series of generations recommences in the next vear and in the same order." 



In the first edition of Professor Owen's 'Lectm"es on the Invertebrata,' published in 

 18i3, however, Morren's errors are adopted, extended, and enunciated as the law of pro- 

 pagation of the Aphides, in the following terms : — 



" In the last generation, which is the seventh, the ninth, or the eleventh, according 

 to the species oi Aphis, the fertilizing influence would seem to have expired J, and deve- 

 lopmental force exhausts itself in more frequent and numerous moultings, in the for- 

 mation of wings, and in the modification of the female organs already described. Many 

 males, which, like the females, acquire wings, form part of the produce of the last brood, 

 which takes place in autumn. They rise in the air, frequently migrate in incalculable 

 numbers, unite, and the females then produce eggs, which are glued to twigs and leaf- 

 stalks, retain their vitality throughout the winter, are hatched in the spring, and give 

 birth to the apterous and larviparous females, which continue to produce successive gene- 

 rations of similar females vmtil the close of summer." (p. 235.) 



It has not been my good fortune to discover, either in Prof. Owen's writings or those of 

 his predecessors, any evidence in support of the singular statement contained in the last 

 paragraph of this citation, which is incorrect in all important respects, and has, indeed, 

 Ijeen omitted in tlie second edition of the ' Lectures.' 



Mr. Walker, in the first of his long and valuable series of papers on the Aphides 

 (Annals, vol. i. 1848, p. 259), writes thus : — 



* "Or chez le puceron du pecher j'ai vu un grand nombre de fois, et j'ai montre le ph&omfene a mon coUegue, 

 M. Burgraeve, ijue la femelle aik'e et propre a la fecoudation ne renfermait point des ceufs et n'en pondait point, 

 mais quelle renfermait des petits pucerons vivants qui naissent tout developpe's avec leurs pattes, leur trompe, et leurs 

 antennes. Ce ne fut qu'en Novembre que les femelles sans ailes pre'sentaient des oeufs dans les ovaries et les oviductes, 

 et pour cela il fallait un froid dejii assez vif." — Morren, I. c. p. 76. 



t Ueber die innereu Geschlechtswerkzeuge der viviparen und oviparen Blattliiusai Froriep's Neue Notizen, 1839. 



% This phrase is little more than a translation of a passage in Morren which will be given below. 



