Fig. 38.—Transverse section through next stage: mk, keel-like mass of cells from which the mesoblast is produced; ec, epiblast. (From Heathcote, Post. Emb. Dev. of Julus terrestris; Phil. Trans. vol. 179, 1888, B.)
Fig. 39.—Longitudinal section through later stage: Segs. 2, 3, etc., segments; Ceph. Seg, head; mes, mesoblast; en, hypoblast; st, future mouth; pr, future anus; mesen, gut; mem.ex, as in Fig. 41. (From Heathcote, Post. Emb. Dev. of Julus terrestris.)
Myriapods are hatched at different stages of development. The Chilognatha have only three appendages, which are so little developed that they are only small shapeless stumps, while the Chilopoda have the full number of legs in some cases; in others only a small number of legs, but yet more than the three pairs of legs of the Chilognatha, and fully developed instead of stump-like. The eyes are usually developed late in the life of the young animal. The bursting of the egg-shell is assisted in some Myriapods by a special kind of spike on the back part of the head.
The Fig. 40 shows a young Chilognath which has just burst the shell and come into the outer world. It is still surrounded with a membrane which has been formed by its skin or epiblast within the egg. One eye-spot has been formed.
Fig. 40.—Young Julus terrestris just hatched.
Fig. 41 shows a longitudinal section through the young Chilognath shown in Fig. 40, and the next (Fig. 42) a transverse section through the same. In comparing the two Figs. 41 and 42 it must be remembered that they are sections in different planes through the animal shown in Fig. 40, and therefore they only show a small portion, a thin slice, of the organs.
