similar at the same time if they have identical genetic sources and close functions, but they are located in different segments. Various pairs of legs of insects and Crustacea are that, for example. In these cases speak about a serial homology (gomodinamiya) as similar structures form ranks (series). When the similar bodies which developed from
numerous from animals in general. The body of insects is accurately divided into the head, a paunch and a breast which are movably connected among themselves. The head consists of Acron and four merged segments surrounded with the general chitinous capsule. Appendages of Acron is pair of antennas, homologous to antenulla of Crustacea. The first segment of the head is reduced therefore the second pair of antennas is not formed. Appendages of other three segments of the head are modified extremities which in the set form the oral device. Are its part: appendages of the second segment – upper jaws, appendages of the third segment – the first pair of lower jaws. Accrete appendages of the fourth segment – the second pair of lower jaws which together form the second unpaired lip. The breast at all insects consists of three segments which are called,, and, respectively,. All of them bear on one couple hodilny feet, and the last two segments bear also on pair of wings. The paunch may contain different quantity of segments, and primitive forms of segments have always more. Extremities on a paunch are absent, but at primitive forms, and also at cockroaches they remain in the form of appendages. The most primitive possess the segmentation close to the gomonomny. The body of all myriapods breaks only into two departments: the head and a trunk which very often consists of very large number of segments from which everything, or nearly all bear on pair of more or less identical extremities.