126 Dr. M. Laurie on the 



cylindrical in shape, are liberally sprinkled with dark yellow 

 curved bristles ; these bristles are not simple, but have three 

 or four small protuberances near the base (fig. 4e). When 

 we come to examine the front end of the embryo we find that 

 the chelicerae are inserted wide apart under the angles of the 

 carapace, and lie sloping towards one another in an almost 

 transverse position (fig, 4 5). From the end of each there 

 runs a thin process, and these two processes lying close 

 together in the middle line pass forward into the appendix, 

 lying dorsal to the central cord. On tracing one of these 

 processes forward in a series of sections, for I have not been 

 able to dissect out the whole of their course, we find it runs 

 as a simple process till it comes to the dilated part of the 

 appendix. On reaching that, however (fig. 4 c?), it expands 

 and bifurcates, forming a pair of somewhat irregular plates, 

 which come into close relation with an oval mass of cells. It 

 is beyond question, I think, that these processes must serve 

 to absorb nutritive material from the surrounding cells. It 

 was impossible to make out any details of the histology of 

 these organs beyond the fact that each plate is formed of a 

 thin outer cuticle, lined by a layer of flattened cells with 

 large spherical nuclei. In the middle there seems to be a 

 space filled with granular material, which may be coagulum. 

 The central cord is thick in the upper part of the appendix, 

 but becomes very small as it runs down towards the embryo. 

 It ends some little way in front of the body of the embryo 

 and is not grasped and masticated by the chelicera3, as in 

 Scorpio. There is no special development of secreting cells 

 round the upper end of the diverticulum, such as we find in 

 Urodacus. 



Opisthocentrus madagascariensis (Kraep.). 



This form is practically the same as Ischnurus. The 

 chelicerge are continued forwards on each side of the central 

 cord into the appendix ; they do not, however, run so far up 

 as in IscJinurns, and the continuations are simple instead of 

 being divided up. These two differences, however, are very 

 possibly due to the embryo being considerably younger. The 

 front of the cephalothorax projects lorward a considerable 

 distance beyond the mouth, and may be partly absorptive in 

 function. The central cord is coiled in the thick part of the 

 appendix and runs back ventral to the chelicerse as far as the 

 mouth. 



