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Updated: May 3, 2025
In the great class of the Crustacea, forms wonderfully distinct from each other, namely, suctorial parasites, cirripedes, entomostraca, and even the malacostraca, appear at first as larvae under the nauplius-form; and as these larvae live and feed in the open sea, and are not adapted for any peculiar habits of life, and from other reasons assigned by Fritz Muller, it is probable that at some very remote period an independent adult animal, resembling the Nauplius, existed, and subsequently produced, along several divergent lines of descent, the above-named great Crustacean groups.
Accepting, then, the type of articulates as founded in nature from the similar modes of development and points of structure perceived between the worms and the crustacea on the one hand, and the worms and insects on the other, have we not a strong genetic bond uniting these three great groups into one grand subkingdom, and can we not in imagination perceive the successive steps by which the Creator, acting through the laws of evolution, has built up the great articulate division of the animal kingdom?
The central and intertropical parts of the Atlantic swarm with Pteropoda, Crustacea, and Radiata, and with their devourers the flying- fish, and again with their devourers the bonitos and albicores; I presume that the numerous lower pelagic animals feed on the Infusoria, which are now known, from the researches of Ehrenberg, to abound in the open ocean: but on what, in the clear blue water, do these Infusoria subsist?
Let us turn then to a wider field, that of the developmental history of the Crustacea, upon which science has already brought together a varied abundance of remarkable facts, which, however, have remained a barren accumulation of unmanageable raw-material, and let us see how, under Darwin's hand, these scattered stones unite to form a well-jointed structure, in which everything, bearing and being borne, finds its significant place.
Here also are some old sponges preserved in flint. Having noticed these beautiful zoophytes, the visitor should proceed in an easterly direction into the room he recently quitted, to examine the table cases it contains. The first tables to which he should direct his attention here, are those in which a series of Crustacea or hard-coated animals are deposited.
These characters absent in the lowest classes Brilliant colours Mollusca Annelids Crustacea, secondary sexual characters strongly developed; dimorphism; colour; characters not acquired before maturity Spiders, sexual colours of; stridulation by the males Myriapoda.
He didn't have time to finish off the class Crustacea through an examination of its stomatopods, amphipods, homopods, isopods, trilobites, branchiopods, ostracods, and entomostraceans.
Of Articulates we find only two classes, Worms and Crustacea. Insects there were none, for, as we have seen, this early world was wholly marine.
If, then, we attempt to map out the Articulata, we must, I think, regard the Crustacea and Insecta as continents, the Myriopoda and Collembola as islands of less importance, but still detached.
Kroyer, whose painstaking care and conscientiousness is recognised with wonder by every one who has met him on a common field of work, confirmed Goodsir's statements in 1846, and, as above mentioned, took out of the brood-pouch embryos advanced in development and resembling their parents. And this, as is well known, applies to nearly all Crustacea.
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