206 87. H. Huzley on the Phenomena of Gemmation. 
but the spores connect the lichen rather with B. vernalis. It 
does not appear to be described. ] 
to Lecidea by Dr. Nylander (Enum. Gen., p. 127) but seems to 
me to be remarkably distinguished by the structure of the apo- 
thecium, and the vermicular spores. 
Art. XXIL—On the Phenomena of Gemmation.—Lecture before 
the meeting of the Royal Institution of Great Britain, by THOMAS 
H. Huxtey, F.R.S.* . 
THE speaker commenced by stating that a learned French 
naturalist, M. Duvau, proposed many years ago, to term the 
middle of the eighteenth century, “l’Epoque des Pucerons:” 
and that the importance of the “phauehusts which. first brought 
to light by the study of these remarkable insects renders the 
phrase “Epoch of Plant-lice,” as applied to this period, far 
~ whimsically inappropriate than it might at first sight seem 
to be 
After a brief sketch of the mode of life of these Plant-lice, oF 
Aphides, as they are technically termed ; of the structure of their 
singular piercing and sucking mouths; and of their relations to 
what are called “ Blights;” the circumstances which have more 
particularly drawn the attention of naturalists to these insects 
were fully detailed. 
It was between the years 1740 and 1750, in fact, that Bon- 
het, acting upon the suggestions of the illustrious Reaumur, 
isolated an Aphis immediately after its birth, and proved to dem- 
onstration, that not only was it capable of spontaneously bring 
ing forth numerous living young, but that these and thelr 
descendants, to the ninth generation, preserved a similar gets f 
_ _ Observations so remarkable were not likely to pass unheeded ; 
but notwithstauding the careful sifting which they have received, 
Bonnet’s results have never been questioned. On the contrary, 
not only have Lyonet, Degeer, Kyber, Duvau, and others, borne 
ample testimony to their accuracy, but it. own that, 
Be fi favorable conditions of tem and , there 18 
pea 20 limit to this power of asexual multiplication, oF 
it has conveniently termed, ‘“‘ Agamogenesis.” _ 
* From the Proceedings of the Royal Institution of Great Britain, May, 1858, 
