Lepidocarpon affords a striking instance of homoplastic modification, for there i s no reason to suppose that the Lycopods were on the line of descent of any existing Spermophyta.
The chances against these two selected members exhibiting another really independent homoplastic agreement are enormous: let us say io,000 to i.
Whilst the chances are in favour of some one homoplastic coincidence or structural agreement occurring between some member or other of a large group a and some member or other of a large group b, the matter is very different 2 a o FIG.
In other words, the Malpighian tubes of the terrestrial Arachnida are homoplastic with those of Hexapoda and Myriapoda, and not homogenetic with them.
The somites following the head are strictly nomomeristic and nomotagmic. The first three form the thorax, thhe appendages of which are the walking legs, tipped with paired claws or ungues (compare the homoplastic claws of Scorpio and Peripatus).