Specimens and Embryo of Opisthophthalmus. 165 
on the whole, larger in proportion at birth than those of the 
other scorpions, but those of Opisthophthalmus are markedly 
so. Newly-hatched specimens of 0. capensis measure 15 mm. 
in length, the length of the mother being 75 mm. They are, 
however, proportionately fewer in number. The cord of cells 
on which the embryo nourishes itself is, on the other hand, 
smaller in Opisthophthalmus than in Scorpio, and~ it is 
probably in relation to these two facts, of the large size of 
the young and the small size of the cord, that we have the 
additional nutritive arrangement of processes from the 
prosomatic region. 
Thorell suggests that the outgrowths from the tail segments 
in the young of Heterometrus are respiratory in function. 
It is quite possible that this is so, and that the prosomatic 
outgrowths of Opisthophthalmus have the same function after 
birth, as the stigmata of the lung-books do not appear to be 
open in these young specimens. 
In such a widespread and ancient group as the Scorpions, 
one is entitled to expect peculiar modifications in many 
respects. In the external structure the variations are 
remarkably small, while the types of development are very 
different. A third type of development seems to exist in 
Vejovis, the eggs of which are comparatively small, and 
apparently devoid of yolk. They develop, however, in the 
ovarian tube like those of Zuscorpius, Androctonus, etc. 
Doubtless many further interesting points exist in various 
species, could one only get the material; but the majority of 
the specimens collected go to our big museums, and, once 
registered in their catalogues, there is but little chance of 
examining their internal structure, 
A further point of interest in connection Sh the newly- 
hatched specimens of Opisthophthalmus is the position of the 
central eyes. In all the Scorpionide these have a somewhat 
posterior position compared with the members of the other 
families. In Heterometrus they are farther back than in 
Scorpio, and in Opisthophthalmus, as its name implies, they 
are very far back, farther back even than in Heterometrus. It 
is interesting, then, to find that in the young individuals the 
eyes approximate to the normal position. Instead of being 
