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1852

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Dana on Crustacea U. S. Exploring Expedition

p. 1411. Size important element in animal life: "as size diminishes in all departments of animal life, the structure changes." A Decapod, as the size diminishes reaches it lower limit: So the Tetrodecapodous, so with Entomostraca.

p. 1487. It is not temperature alone or mainly which determines the depth to which species live. (The Boreal deep-w. species found in Mediterranean, he asserts are, also, deep-w. in North seas.)

p. 1501. The Brachyura, though most numerous in the torrid zone, do not reach in this zone their highest perfection. The Temperate seas are the habitat of the higher species (I must think this highness & lowness are rather fanciful) p. 1502

 

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p. 1502 the degradation of the maioides takes place in warm-water: the degradation of  Canaroides (both Brachyura) is reversed.

p. 1528. The species of highest rank in the Brach, Microsura, Isopoda, & Amphipoda are extra-torrid zone.

p 1529.  A preponderance of species in the warm seas is perhaps to be expected, since warm waters have prevailed even more largely than now in earlier epochs (? remember glacial period).

p 1529.  None of the Maioides, the highest of the Crustacea, have yet been reported from any Geological series.

p. 1567. Japan & the Mediterranean have several obviously representative species; 4 species identical & one or two others hardly distinguishable  How are shells.

This remarks already made by De Haan.

Remember my Poecilasma, & Fish.

 

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p. 1574.  list of 16 species common to Natal & S. Japan, or the Hawaiian Group districts, & not found yet in the intermediate torrid region.

p. 1578 New Zealand has almost as much affinity with Chile as with Australia, two species in common: Cancer a genus found there, but  where else beyond America & Europe. M. Edwards has observed a Palaeomon affinis of N.Z. hardly distinguishable from one of Europe (Plaguria tomentosa common to N.Z. Chile & S. Africa.) the species of Portunus are representative of those of Europe.

Study oceanic currents

(Can northern forms have travelled down E. or W. America to the south & thence to N. Zealand ????.)

p. 1583. Clearly allied species at Chile & N. S. Wales.

p. 1579 with our existing Knowledge the Arctic & Antarctic crustacea "widely differ", (because intermediate seas never arctic).

 

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p. 1584. Galene natalensis found at Natal & at Hawaii, & not in intermediate seas & represented by another species at S. Japan. - - Admits as just possible that some species might have been floated through torrid zone in one season (or died out subsequently in intermediate regions) from Japan to Natal, but doubts this cd have taken place with the above Galene

p 1585. says just possibly that Plaguria tomentosa may have migrated from N.Z. S. Africa (but some difficulty of getting into Western current from Laguthes current. & America (5000 N.Z. to S. America); During glacial period Fauna further north & the islands between?

says intermediate isld. wd have helped, but no fact to support such an hypothesis. (? plants).

p. 1585 a very few species common to E. & W. coast of America. - one common to Brazil & Chile, another to Valparaiso. W. Indies & Canaries

 

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p. 1586 - When we find 2 temperate regions having no water communication, except through torrid zone, yet having closely allied & identical species as in Japan & Mediterranean, we must deny migration voluntary or involuntary; even if we break through isthmus of Suez, still we enter only torrid seas. The resemblance in this above case is not only of a few identical species, but there are genera in both, which occur nowhere else. & some species are closely allied Now this resemblance of genera & species, without exact identity in the latter, is not explained by possible communication; (N.B it is important that we have seen several cases of few species identical where there are genera & species allied.) but we may reasonably account for it by

 

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similarity of physical condition – "like causes, like effects." – "identical circumstances will necessarily imply identity of genera in a given class & even of specific structure or of sub-genera."

p. 1587. (so admits of double- creations, at Japan & Mediterranean - so in New Zealand & Britain, "we must appeal directly to creative agency for the peopling of N.Z. seas, as well as the British" – "it is certainly a wonderful fact that N.Z. shd have a closer resemblance in its Crustacea to G. Britain, its antipodes, than to any other part of the world, - a resemblance running parallel with its geographical form" &c &c conditions.

According to present appearances West coast of S. America was - probable channel of [commerce] cd the few that are common to Chile & Brazil have all come from North.

p. 1588. "When we find the same species in regions of unlike physical character", as for

 

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example G. Britain & Canary Isd or Mediterranean, "we have strong reasons for attributing the diffusion of the species to migration." - These regions "are so far different that we may doubt whether species created independently in the two, could have been identical, or even had that resemblance that exists between varieties" (This, his argument kills, I think, his former one of identical species having been created for identical districts, for it shows them in no such very close relation of species & conditions.)

p 1589 very few species common in Oriental & occidental torrid zone, yet conditions seem to be the same; this favour view that the

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wide distribution of Oriental species - due to migration & not to creation; for otherwise we shd have had similar creations in occidental & oriental seas, the conditions being apparently the same.

p. 1590 Hints that the creation of lower animals, these being simpler, might be identical in two regions, but not in the higher, from which higher & more complicated organisms it may be inferred still closer identity of conditions wd. be required –admits that migration has had great influence amongst Crustacea

p 1590. "There is evidence in the exceedingly small number of torrid zones species identical in the Atlantic & Indian oceans, How in shells & Fish? that there has been no water communication, across from one to the other in the torrid zone, within the existing period,"

/over

 

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This agrees with my view, for during glacial period they wd. have been still less likely to have crossed by Red Sea or C. of Good Hope.

 

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Dana's argument of "like causes, like effects", apparently at first good, but surely if so we shd expect to find generally where conditions like, species like: compare volcanic isld in torrid zone - compare Fuegia with N. Scotland - Tasmania with France. Arctic with Antarctic Moreover we shd expect some gradation in relation: Australia S. America not eminently unlike other parts of world, yet eminently peculiar in Fauna. Moreover species generally are not adapted so closely to peculiar conditions, & they range far, & are capable of introduction into new countries. as might be inferred if creation accounted for by close similarity of conditions. No doubt each species in each habitat closely adapted but this owing to struggle from all its inhabitants havng widish range of adaptation. Some exceptional cases of same species where apparently no means of migration ought not to upset the general conclusion that no very close relation between conditions & species old-standing.

Barriers seem leading cause of difference.