164 Proceedings of the Royal Physical Society. 
The eggs of most scorpions contain, like those of other 
Arachnids, a large amount of yolk, on which the embryo 
nourishes itself during development. This is the case, 
roughly speaking, in the families of the Buthide, Bothriuride, 
and Ischnuride,! and in all these the egg early leaves the 
follicle in which it is formed and fertilised and passes into 
the ovarian tube of the mother, where it undergoes the 
oreater part of its development.? In the family Scorpionide, 
however, the egg is very small and contains no food-yolk. 
It is formed at the end of a long diverticulum of the ovarian 
tube, and develops in situ, the embryo gradually extending 
downwards till it occupies the whole of the diverticulum.? 
It does not leave this position until it is fully developed. 
The nutrition of the embryo in these forms is provided for 
in the earliest stages by secretion from the cells lining the 
diverticulum. Later the embryo feeds on a solid cord of 
cells which terminates the diverticulum, which it crushes 
betwixt the chelicere. In connection with this mode of 
nutrition, the chelicersee are developed long before the other 
appendages, and provided with a chitinous plate on the 
inner surface of the last joint. In the ordinary scorpions 
(Euscorpius, Centrurus, etc.), on the other hand, the develop- 
ment of the chelicere is delayed, and while the rest of the 
appendages appear in order from before backwards, the 
chelicerze do not appear till after the other five prosomatic 
appendages. In Opisthophthalmus the modification of the 
cheliceree for this function has produced a most abnormal 
structure (Fig. 8), the last joint being enlarged out of all 
proportion, and distorted in shape. The chitinous plate on its 
inner surface is somewhat smaller and simpler than in Scorpio. 
The later embryos of Scorpio fulvipes have dorsal out- 
growths similar to those of Opisthophthalmus, and there is 
little doubt they serve to absorb nourishment from the 
surrounding tissues. The young of the Scorpionide are not, 
1 For a list of the forms in which the different modes of development occur, 
see Annals and Mag. Nat. Hist., March 1896. 
2 Brauer, Zeitschr, wissensch. Zoologie, vols, lvii. and lix.; and Laurie, 
Quart. Jour. Micros. Soc., vol. xxxi. 
3 Laurie, Development of Scorpio fulvipes, Quart. Jour. Micros. S: c., vol. xxxii. 
