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Sept 47— What a vast range of character in the Branchipoda & Entomostraca, (which are embryonic groups?—) compared with the Podophthalma & Edriothalma.— So in plants what a diversity in the lower orders — So in fish a great range in the lower or near progeny have embryonic forms.— Waterhouse remarked that in all low groups parts of great group, characters are of less value, ie more variation— ie more broken groups.— If we get more varied characters, it implies more extinction: hence most low groups & therefore probably first formed have suffered most extinction.

Had better be stated, that those parts of groups which are known to be the oldest, & those which are lowest & which as general rule are the oldest (known to be case with plants) are most broken — Fish Cartilaginous fish though oldest are not lowest, but embryonic.— Are not the Cephalopods much broken, case of fish.—

How come it that highest ↘

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Fish & Mollusca have been exterminated & Reptiles

The sea once occupied by Reptiles, those fish most related to reptiles & by the highest mollusca — how came it, that its present inhabitants are lower? We must except Cetacea & seals— The Mollusca oddest case.— Have crustacea anything to do with this?

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