Studies in the Theory of Descent, Volume II

According to my view this would be a case of the reversion of the Triton to the immediately anterior phyletic stage, _i.e._ to the perennibranchiate stage, and in the present in...

Thus the supposition is not wanting in support, that peculiar conditions make it more difficult for the creature to obtain its food upon land than in the water, and this alone m...

In the first place it must be said that the positive basis of this hypothesis is insecure. Cases of sudden transformation of the whole organism with subsequent inheritance are a...

The matter becomes still more enigmatical through the fact that the gland, although present, is quite rudimentary. Whilst in the _Salamandrina_ the capacious intermaxillary cavi...

Edward von Hartmann may justly claim that his views should be considered and tested by naturalists.[287] He would be correctly classed with those philosophers who have approache...

In _Smerinthus Tiliæ_, _Ocellatus_ and _Populi_ also, the greatest larval variability is shown only in the last stage, the preceding stages being very constant. These cases by n...

In this same family of the _Sphingidæ_ cases are not wanting in which, on the other hand, the moths are far more closely allied than the larvæ. This is especially striking in th...

Mr. C. V. Riley in his “Second Annual Report on the Noxious, Beneficial, and other Insects of the State of Missouri, 1870,” gives figures and describes the early stages and adul...

Fig. 41. Stage IV.; the same larva after the third moult. Transformation of the ground-colour from green to black, owing to the spread of the black patches proceeding from the r...

It is just cases of this last kind, however, which are best fitted for exposing the improbability and insufficiency of the assumption of a variational tendency as a distinct dir...

The imagines of the Diptera (_genuina_), with the exception of the _Aphaniptera_ and _Pupipara_, agree in all their chief characters, such as the number and structure of the win...

Incongruences of this last kind appear in certain cases within families (_Nymphalidæ_), but I will not now subject these to closer analysis, because their causes will appear mor...

I believe that I have shown that the theory of selection by no means leads--as is always assumed--to the denial of a teleological Universal Cause and to materialism, and I there...

[247] [Eng. ed. It has frequently been objected to me that the existing Axolotl is not a form resulting from atavism, but a case of “arrested growth.” The expression “atavism” i...

It would be meaningless to assert that the two stages above mentioned were _completely_ independent of one another. It is obvious that the amount of organic and living matter co...

Without going at present into the causes of these phenomena I will pass on to the consideration of further facts, and will now proceed to investigate both the form-relationships...

Meanwhile, in the absence of further observations, we must admit that the Paris Axolotls were not _Siredon Lichenoides_, but some nearly allied and probably new species. But lit...

Mr. C. V. Riley states[219] with reference to the larva of _Thyreus Abboti_ that the ground-colour appears to depend upon the sex, Dr. Morris having described the insect as “red...

The fact of individual variability can in this way be well understood; the living organism contains in itself no principle of variability--it is the _statical element_ in the de...

In this case also the difference in the value of the systematic groups formed by the two stages corresponds precisely with the difference in the conditions of life. This appears...

_Araschnia._ _A. levana_ and _A. prorsa_ seasonally dimorphic, 2; dimorphism of larvæ, 6; _A. levana_, first experiments with, 10; _A. var. porima_, artificial production of, 10...

_Vanessa._ _V. Urticæ_, climatic variation, 60; _V. Atalanta_, _Urticæ_, and _polychloros_, variable in two stages, 405; _V. Io_, variable in one stage, 407. Congruence and inco...