Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 20, 2025
A pentacrinoid Echinoderm, with a complete jointed stalk, is developed within the larva of Antedon. Is it not possible that the larva of Crossopodia may have developed a vermiform Echinoderm? With respect to the Phylogeny of the Arthropoda, I find myself disposed to take a somewhat different view from that of Professor Haeckel.
If a 'Bipinnaria', a 'Brachialaria', a 'Pluteus', is competent to produce the Echinoderm, which is so widely different from it; if a hydroid polype can produce the higher Medusa; if the vermiform Trematode 'nurse' can develop within itself the very unlike 'Cercaria', it will not appear impossible that the egg, or ciliated embryo, of a sponge, for once, under special conditions, might become a hydroid polype, or the embryo of a Medusa, an Echinoderm."
There is no more difficulty in understanding how the branched spines of some ancient Echinoderm, which served as a defence, became developed through natural selection into tridactyle pedicellariae, than in understanding the development of the pincers of crustaceans, through slight, serviceable modifications in the ultimate and penultimate segments of a limb, which was at first used solely for locomotion.
If a 'Bipinnaria', a 'Brachialaria', a 'Pluteus', is competent to produce the Echinoderm, which is so widely different from it; if a hydroid polype can produce the higher Medusa; if the vermiform Trematode 'nurse' can develop within itself the very unlike 'Cercaria', it will not appear impossible that the egg, or ciliated embryo, of a sponge, for once, under special conditions, might become a hydroid polype, or the embryo of a Medusa, an Echinoderm."
Hence a sudden arrest of the entire animal world in its progress towards higher and higher mobility; for the hard and calcareous skin of the echinoderm, the shell of the mollusc, the carapace of the crustacean and the ganoid breast-plate of the ancient fishes probably all originated in a common effort of the animal species to protect themselves against hostile species.
"It's an echinoderm," he said, "generally with five arms, that lives only in the sea, has a simple stomach, and feeds on the minute organisms in the water." "There you're wrong," said the director. "It lives only in the sea, that's right enough, but you haven't proper regard for a starfish's powers of digestion. It feeds on mussels, oysters and other shellfish. Can it swim?"
Their development is obscure, but it must be remembered that the rocks only give the record of shore-life, and only a part of that is as yet opened by geology. Some experts think that they were developed in inland waters. The quaint stalked Echinoderm which also we noticed in the Cambrian shallows has now evolved into a more handsome creature, the sea-lily.
I cannot believe that the Isthmus of Panama has been open since the commencement of the glacial period; for, notwithstanding the fishes, so few shells, crustaceans, and, according to Agassiz, not one echinoderm is common to the sides. I am very glad you are going to publish all your papers on Natural Selection: I am sure you are right, and that they will do our cause much good. Eheu! Eheu! Eheu!
The fossil records of the long ages during which the Mollusc, the Crustacean, and the Echinoderm slowly assumed their characteristic forms are hopelessly lost. But we are now prepared to return to the record which survives, and we shall find the remaining story of the earth a very ample and interesting chronicle of evolution.
Word Of The Day
Others Looking