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Geograph. Distrib. (on Single & Double Creations.)

(Always bear in mind this refers to identical species)

Great & important subject — Most obvious point — if no creation all identical, (not now to mention allied forms,) must have descended from common parents & therefore have come from one point. This is question largely discussed of single & double creation. The question turns much on whether in most cases identical forms live near each other, or whether far for: those who believe in single creations speak of few exceptions: those who believe in double say truly that the exceptions are very numerous & inexplicable.

 (Cd it be proved that some species created at 2 separate spots wd upset my theory)

(The father & the child must stand or have stood in proximity)     

(My argument in respect to 4 or 5 grand divisions of world, applicable only to forms. It is different question whether many individuals of species created.)

[in margin:] Many of the discussions will come into play on other topics

Before details & discussing disconnected oceans I think some light will be thrown by considering whether any general facts point to any general conclusions. –I think there are (see separate Paper) (1 bis) distribution not explained by conditions

(1)  Barriers. (2)  Continuity of areas, which is related to last in Plants (3)  probability of disconnection from extinction & accidental diffusion & ignorance of means of diffusion (4) distribution of mammalia relation to soundings (5) analogy from time not here to be discussed.

(1) The area of each species generally, (as remarked by Forbes) continuous without Barriers – Decandolle, Mammalia in Physical Atlas — I believe in shells — But the question is exceptions, how numerous; especially when we consider islds. If continuous from one point, origin of idea probably (shape of areas from Decandolle); for Physical conditions do not go by continuous areas. ['continuous areas' in right margin]

(2) condition will not account for distribution La Plata, though so thought by very best observers; but there may be other Law.

(3) extinctions & accidental diffusion will account for some disconnection.

(4) Effect of Barriers, intricately connected with continuous areas, but yet somewhat different, if we find as general rule that in regard, to means of distribution that barriers separate groups of species, independently of conditions we are led to conclude that species created that existed on each side of barrier — this begins with plants from Decandolle.

(5) Mammalia

(6) special cases: plants on islands: aquatic plants: land Mollusca: F. water fish alpine plants & animals: S: hemisphere.— S. hemisphere crustacea & Bryozoa. (?Generally inhabitants of islands.)

(6) analogy from geological changes of species less important because one does not know past conditions.

[insertion:]  I think I shall allude to this sufficiently when showing same conditions do not give same species.

 

[in margin:] This ought to come after the general views.

 

Probably most will agree that single productions the rule, double the exception. One of the most simple cases, plants of islands — not united to continents, for if so almost every isld in ocean united within recent period. Continents must commence – they are volcanic, they are rising, they are not fragment of continents deep-sea-soundings changes great, yet continents were continents in later Tertiary periods — Then discuss means of dispersal – Then glacial period Then aquatic plants — Then F.W. Fish — Then land Mollusca — Frogs & Reptiles.

[89v]

The question whether 1 or more parents distinct — in a flock of improved Southdown; you cannot say that any one was parent.

Johnston's Atlas wd show whether Mammalia had continuous or disconnected Ranges

In cases where Plants very different without Barriers, we have Australia forming 2 islds.  some spread – preoccupation – Siberia, colonised after glacial period from south from very different regions.