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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.
Formerly, to describe this group, people said 'articulate animals, an expression which possessed the drawback of not jarring on the ear and of being understood by all. This is out of date. Nowadays, they use the euphonious term 'Arthropoda. And to think that there are men who question the existence of progress! Infidels!
The next higher examples to be met are the frequently cited ants and bees, belonging to the lowly organized class of arthropoda, yet, through the advantage of association and mutual aid, developing actions and habits only found elsewhere in the human race. The only example among vertebrates is that of the beavers, members of the low order of rodents.
Say, 'articulate, first; then roll out, 'Arthropoda; and you shall see whether zoological science is not progressing! In bearing and colouring, Epeira fasciata is the handsomest of the Spiders of the South. On her fat belly, a mighty silk-warehouse nearly as large as a hazel-nut, are alternate yellow, black and silver sashes, to which she owes her epithet of Banded.
The other group or Phylum of animals with which we will be particularly concerned is known as the Arthropoda, which means "jointed-feet" and includes the crayfish, crabs, spiders, mites, ticks and insects. Of these only the last three are of interest to us now.
Aristocracy, increased beauty of the. Arms, proportions of, in soldiers and sailors; direction of the hair on the. Arms and hands, free use of, indirectly correlated with diminution of canines. Arrest of development. Arrow-heads, stone, general resemblance of. Arrows, use of. Arteries, variations in the course of the. Artery, effect of tying, upon the lateral channels. Arthropoda.
From some of these "Zoeopoda" arose all the remaining Malacostracous Crustacea; while, from others, was developed some form analogous to the existing Galeodes, out of which proceeded, by gradual differentiation, all the Myriapoda, Arachnida, and Insecta. I should, be disposed to interpret the facts of the embryological history and of the anatomy of the Arthropoda in a different manner.
By the structure of the abdomen in Nauplius we might be reminded, like Oscar Schmidt, of the moveable caudal fork of the Rotatoria, which many regard as near allies of the Crustacea, or at any rate of the Arthropoda; in the six feet surrounding the mouth we might imagine an originally radiate structure, and so forth. But I can see nothing certain.
The higher group includes the crabs, spiders, thousand-legs, and finally the insects, and forms the kingdom of arthropoda. The lower members are still usually reckoned as worms, and are included under the annelids. Of these our common earthworm is a good example, and near them belong the leeches. But the marine annelids, of which nereis, or a clam-worm, is a good example, are more typical.
The session begins with a brief off-hand discussion of the general characteristics and affinities of the group of arthropoda, of which the crawfish is a member.