Specimens and Embryo of Opisthophthalmus. 163 
structure, like the preoral process, is hollow, and is filled 
with trabecular tissue and blood-vessels. 
A further point which we may note in these newly- 
hatched specimens is the presence on certain of the tail 
segments (8th to 11th free segments) of paired bladder, like 
outerowths from the dorsal surface. Similar structures 
have been described by Thorell as being present on 
some young specimens of the closely allied genus 
Heterometrus. 
Among some adult specimens of Opisthophthalmus 
capensis, for which I am indebted to Mr Peringuey of 
the Cape Town Museum, I was fortunate enough to find a 
female containing embryos in a late stage of development. 
One of these is figured in Figs. 5-7, and we see that at 
this stage there is a very prominent horn-like structure 
- arising from the back of the carapace. Careful examination 
shows this horn to be composed of two parts, lying one 
behind the other. The anterior, which forms the greater 
part of the horn, arises (Fig. 7) in front of the mouth, and 
bends back over the front of the head to join the posterior 
part. This posterior part arises from the dorsal surface of 
the cephalothorax, and extends for about half of the length 
of the anterior part, lying close to it, but apparently separate 
throughout. The horn formed by these two processes 
penetrates through the thick walls of the follicle round 
the cephalothoracic region, and projects freely among the 
tissues of the mother. 
The 2nd to 7th free segments of these embryos are swollen 
out dorsally into large paired oval outgrowths, while the 
Sth to 11th segments bear smaller but similar structures. The 
last segment is free from any trace of outgrowths, and has 
the normal cylindrical form. While the follicle surrounding 
the cephalothoracic (prosomatic) region of the embryo is 
very thick and strong, that surrounding the free segments 
is very thin. 
The most probable function of the horn-like prosomatic 
and bladder-like meso- and metasomatic outgrowths is that 
of absorbing nutriment for the embryo from the surround- 
ing tissues of the mother. 
