DEVELOPMENT OF THE CAPE SPECIES OF PERIPATUS. 379 



matter beneath the ectoderm, all become distinctly apparent 

 at about the same time iu Stage g ; but how and when they 

 are developed I am unable to say. As may be seen from an 

 inspection of the sections (Part III, figs. 37 — 39) there is in 

 Stage f a certain amount of this fibrous tissue, especially at 

 the ventro-lateral corners of the body, close to the outer border 

 of the nerve-cord, and in the nerve-cords themselves as the 

 white matter, and I have no doubt that it is present at a still 

 earlier stage, though masked by the large amount of nuclei 

 present. In fact, it may be said of this tissue generally, that 

 it does not become a marked feature of the sections until the 

 organs separate from one another and leave room for the pre- 

 viously closely-packed nuclei to spread out, and, as in the case 

 of the white matter of the nerve-cord, partly to withdraw them- 

 selves from it (cf. PI. XXVI, fig. 5, and Part III, fig. 39). In 

 whatever manner this tissue may be developed, I think there can 

 be little doubt that it is from its first appearance a continuous 

 tissue, that is to say, the circular fibres at circ. muse, in PI. 

 XXVI, fig. 5, are continuous with the network at neuro-musc, 

 which, in its turn, is continuous with the bundle of fibres forming 

 the nerve, and so with the fibrous matter of the nerve-cords. It 

 thus appears, so far as I have been able to observe the develp- 

 ment, that the nerves are not formed as outgrowths from the 

 central nervous system, but are parts of a network which 

 originally existed when the nerve-cords were part of the 

 surface ectoderm. In Stage g, the network is clearly con- 

 tinuous with the surface ectoderm (PI. XXVI, fig. 5). With 

 regard to the commissures connecting the ventral nerve-cords, 

 it seems to me that they also are differentiated in situ from the 

 median ventral ectoderm at a time when the nerve-cords were 

 still parts of the surface ectoderm. I have already said that I 

 do not know the manner in which this network develops ; part 

 of it is undoubtedly formed around the ectodermal nuclei, e. g. 

 the white matter of the cords, the commissures between the 

 cords ; some of it, on the other hand, has, from the first, a 

 relation to the mesodermal nuclei, e. g. the circular fibres at 

 circ. muse, and the network on the ventral side of the feet at 



