360 



PSEUDOSGORPIONIDJE. 



The eggs after being laid are carried by the female attached to the first 

 segment of the abdomen. The segmentation (vide p. 93) is intermediate 

 between the types of complete and superficial segmentation. The ovum, 

 mainly formed of food-yolk, divides into two, four, and eight equal segments 

 (fig. 197 A). There then appear one or more clear segments on the surface 

 of these, and finally a complete layer of cells is formed round the central 

 yolk spheres (tig. 197 B), which latter subsequently agglomerate into a 

 central mass. The superficial cells form what may be called a blastoderm, 

 which soon becomes divided into two layers (fig. 197 C). There now 

 appears a single pair of appendages (the pedipalpi) (fig. 198 A, pd), while at 

 the same time the front end of the embryo grows out into a remarkable 

 proboscis-like prominence a temporary upper lip (concealed in the figure 

 behind the pedipalpus), and the abdomen (ab) becomes bent forwards to- 

 wards the ventral surface. In this very rudimentary condition, after under- 

 going an ecdysis, the larva is hatched, although it still remains attached to 

 its parent. After hatching it grows rapidly, and becomes filled with a 

 peculiar transpai'ent material. The first pair of ambulatory appendages is 

 formed behind the pedipalpi and then the three succeeding pairs, while at 

 the same time the chelicera? appear as small rudiments in front. External 

 signs of segmentation have not yet appeared, but about this period the 

 nervous system is formed. The supra cesophageal ganglia are especially 



FIG. 196. THREE STAGES IN THE DEVELOPMENT OF THE SCORPION. THE EMBRYOS 



ARS REPRESENTED AS IF SEEN EXTENDED ON A PLANE. (After Metschllikoff.) 



<:/;. chelicerae; pd. pedipalpi; p l p*. ambulatory appendages; pc. pecten ; st. 

 stigmata; ab. post abdomen (tail). 



distinct, and provided with a central cavity, probably formed by an invagi- 

 nation as in other Arachnida. In the succeeding stages (fig. 198 B) four 

 provisional pairs of appendages (shewn as small knobs at ab) appear behind 



