ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 57 
leads us; it remains only to consider the second. If it be true, the 
occurrence of agamogenesis in the animal kingdom must bear an 
approximatively inverse ratio to the complexity of the organization 
of the different groups. Let us examine one or two sub-kingdoms in 
this point of view. Among the Aznulosa, the Rotifera and Turbellaria 
possibly possess it to a small extent ; the ematozdea do not possess 
it at all. Many Zrematoda possess it; others, such as Aspidogaster, 
have nothing of the kind. The Acanthocephala are not known to. 
possess it; the Echznodermata are regarded by Professor Owen as 
possessing it, but their different families show every gradation from 
simple metamorphosis to something like agamogenesis. A few 
Annelida possess the power in a marked degree; in many, nothing 
of the kind is known. The JVazs has it; the Earth-worm and the 
Leech have it-not. Of the Crustacea, some, such as many Branchio- 
poda, exhibit it in the highest perfection; but no trace of it has yet 
been found in Copepoda, Cirripedia, Pectlopoda, Edriophthalmia, or 
Podophthalinia. In the Myriapoda and Arachnida the process is not 
known: but we find it in the highest Artéculata—the Inusecta—and 
this not, so far as we know at present, in Aptera or Orthoptera, but in 
a few Hemiptera, Hymenoptera and Lepidoptera; and there is every 
reason to believe that it only occurs in isolated, though perhaps in 
many, genera of these orders. Take the J/odlusca again: agamogenesis 
occurs in the Polyzea and Ascidioida, not in the Brachiopoda.. It is 
not known to occur in any of the Lamelltbranchiata ; and among the 
higher JZol//usca the nearest approach to it is presented by the animal 
(whatever it is) which gives rise to the “Synapta-schnecken” (high 
Gasteropods), and by the Hectocotyligenous Cephalopoda. 
After this simple statement of well-known facts, I need not remind 
even the tyro in zoology, that there is no evidence of an inverse 
relation between the occurrence of agamogenesis and complexity 
of organization. 
I have hitherto, in the course of this argument, confined myself in 
the main to the development of Aph7s ; but it is only just to observe 
that the author of the hypothesis brings forward yet another original 
observation in support of his large generalization :— 
“In the freshwater polype, the progeny of the primary impregnated 
germ-cell retained unaltered in that body, may set up, under favour- 
able stimuli of light, heat, and nutriment, the same actions as those to 
which they owed their own origin; certain of the nucleated cells do 
set up such actions, those, e.g. in the Hydra fusca, which are aggregated 
near the adhering pedicle or foot ; and the result of their increase by 
assimilation and multiplication is, to push out the contiguous integu- 
