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It degenerates, but still is easily recognized as a worm. A crustacean tries the same experiment, though living outside of its host instead of in it. It sinks to a place even lower, if possible, than that of the parasitic worm. A locomotive form becomes sessile.
This was a sore trouble to me, adding, as I then thought, one more instance of the abrupt appearance of a great group of species. But my work had hardly been published, when a skilful palaeontologist, M. Bosquet, sent me a drawing of a perfect specimen of an unmistakable sessile cirripede, which he had himself extracted from the chalk of Belgium.
Hence we now positively know that sessile cirripedes existed during the secondary period; and these cirripedes might have been the progenitors of our many tertiary and existing species. The case most frequently insisted on by palæontologists of the apparently sudden appearance of a whole group of species, is that of the teleostean fishes, low down in the Chalk period.
In a memoir on Fossil Sessile Cirripedes, I have stated that, from the number of existing and extinct tertiary species; from the extraordinary abundance of the individuals of many species all over the world, from the Arctic regions to the equator, inhabiting various zones of depths from the upper tidal limits to 50 fathoms; from the perfect manner in which specimens are preserved in the oldest tertiary beds; from the ease with which even a fragment of a valve can be recognised; from all these circumstances, I inferred that had sessile cirripedes existed during the secondary periods, they would certainly have been preserved and discovered; and as not one species had been discovered in beds of this age, I concluded that this great group had been suddenly developed at the commencement of the tertiary series.
Hence we now positively know that sessile cirripedes existed during the secondary period; and these cirripedes might have been the progenitors of our many tertiary and existing species. The case most frequently insisted on by palaeontologists of the apparently sudden appearance of a whole group of species, is that of the teleostean fishes, low down in the Chalk period.
Of course we, as animals, naturally hold that it is better to go about in search of what we can find than to sit still and make the best of what comes; but there is still so much to be said on the other side, that many classes of animals have settled down into sessile habits, while a perhaps even larger number are, like spiders, habitual liers in wait rather than travellers in search of food.
The cherry is the next wild fruit which claims our attention, and of this we find two varieties. This fruit is also called in some countries coroon, from corone, a crow. Its flowers are in nearly sessile umbels of the purest white; its leaves broadly lance-shaped and downy beneath, pointed and serrated, with two unequal glands at the base.
If the tumour is seated close to the membrana tympani, and has a broad and sessile base, then it cannot be excised or noosed with any degree of success. It must therefore be treated by the daily application of the solid nitrate of silver, applied exactly to its surface; and, in the intervals of application, the use of any collyria may be had recourse to.
And one day I caught Winnenap' drawing out from mid leaf a fine strong fibre for making snares. The borders of the iris fields are pure gold, nearly sessile buttercups and a creeping-stemmed composite of a redder hue. I am convinced that English-speaking children will always have buttercups.
Systematic affinity suggests that the "three leaved" forms must have been derived from pinnate ancestors, evidently by the reduction of the number of the leaflets. In some species of clover the middle of the three is more or less stalked, as is ordinarily the case in pinnate leaves; in others it is as sessile as are its neighbors.
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