They are machines, Greenly, and have their laws, just the same as the planets in the heavens. The idea comes from a fish, head, run, and helm; and all we have to do is to study the fishes in order to get the sort of craft we want. If there is occasion for bulk, take the whale, and you get a round bottom, full fore-body, and a clean run.
The sequence of the sections of the body in order of time seems originally to have been, that first the fore-body, then the hind-body, and finally the middle-body was formed. This is a circumstance which renders very doubtful the equivalence of the middle-body of the Malacostraca with the section of the body which in the Copepoda bears the swimming feet and in the Cirripedia the cirri.
None of these attempts has ever met with general acceptance; my own investigations lead me to a conception which nearly approaches Van Beneden's. I assume four sections of 5 segments each the primitive body, the fore-body, the hind-body, and the middle-body.
When you want speed, models are plenty take the dolphin, for instance, and there you find an entrance like a wedge, a lean fore-body, and a run as clean as this ship's decks. But some of our young captains would spoil a dolphin's sailing, if they could breathe under water, so as to get at the poor devils. Look at their fancies!
It is to be supposed that, not only originally but even still, in the larvae of the first Malacostraca, the new body-segments and pairs of limbs are formed singly, first of all the segments of the fore-body, then those of the abdomen, and finally those of the middle-body, and, moreover, that in each region of the body the anterior segments were formed earlier than the posterior ones, and therefore last of all the hindermost segment of the middle-body.
If one only thinks about it, one can observe that the island is a butterfly. Toward the north, the slender fore-body and the round head can be seen, and toward the south, one sees the back-body which first broadens out, and then narrows to a sharp point." Here he paused once more and looked at his companion rather anxiously to see how he would take this assertion.
The sky was of a beautifully clear, rich blue tint, flecked here and there with thin, fleecy, fine weather clouds; the monsoon swept down upon their port bow in a cool gush, redolent of the exhilarating smell of the open ocean, a very life-giving tonic; and the long, low mounds of the Pacific swell, wrinkled with the sweep of the breeze, just sufficed to give life in a long, easy plunging movement to the hull of the Flying Fish, at one moment lifting her sharp-pointed nose and some twenty feet of her fore-body clear out of the blue, sparkling brine, and anon causing her to dive into the on-coming undulation until she was buried nearly midway to her superstructure.
The large compound eyes, which usually soon become moveable, and sometimes stand upon long stalks even in the earliest period, as well as the carapace, which covers the entire fore-body, indicate at once that the position of the larvae hitherto considered, notwithstanding all their differences, is under the Podophthalma.