求翻译：向前运动过程中，以4→2→1→3的顺序依次向前移动步足，未移动的步足伸展或收缩推动蟹身的向前运动。是什么意思？

The In in the of the forward movement of the process of, in order to the 1 → 3 the order of of the 4 → 2 → in turn forward mobile pereiopod, that were not moved pereiopod stretching or contraction to to promote the the the the forward movement of of the crab the body of.

In the process moving forward, in order to 4→2→1→3 in order to move forward step by step is not moving enough to extend or retract the crab moving forward.

Forward in rate process, by 4→2→1→3 smooth in turn forward motion ambulatory leg, motion ambulatory leg extension or contraction impetus crab body forward movement.

Forward during exercise, with 4 → 2 → 1 → 3 forward step foot in the order, is not moving step foot stretch or shrink to promote forward movement of the shells.

正在翻译，请等待...