Anatomy of some Scorpions. 189 



have as yet failed to trace this longitudinal nerve to its 

 termination at either end. 



Examination of the nerve-cord shows, then, that we can 

 get no aid from it in classifying the Scorpions. The position 

 of the ganglia seems to vary quite independently of the 

 relations of the species to one another, as may be seen by 

 comparison of the figures, such unquestionably nearly allied 

 forms as Scorpio (fig. 3) and Palamnceus (fig. 2) showing 

 great differences. On the other hand, the segments supplied 

 by each ganglion remain the same throughout. The position 

 of the ganglia might serve as a generic character, but is of no 

 greater value. 



The varying position of the dorso-ventral muscle of the 

 first metasomatic (thirteenth) segment might also be useful 

 as a generic character, but here also we get considerable 

 differences in closely allied forms. 



II. The Reproductive Organs. 



As nearly all my material was procured with the idea of 

 further elucidating the embryology of these forms, I have not 

 had much opportunity of examining the male organs, and 

 will therefore postpone any account of them to some future 

 time. The general anatomy of the female organs is suffi- 

 ciently well known, and the only point of importance in which 

 the various forms differ is that of the structure of the egg, 

 and, in relation to this, the mode of formation of the embryo. 

 The two types of development have been described in detail 

 elsewhere, and seem to me to constitute a difference of very 

 considerable morphological importance. 



In the first type of development * the egg is of consider- 

 able size, and contains a large quantity of yolk (fig. 7) . It 

 passes at an early stage out of the follicle in which it is 

 formed and fertilized into the ovarian tube (fig. 8), in the 

 cavity of which it undergoes the greater part of its develop- 

 ment. Two embryonic membranes are formed round the 

 embryo, and it appears to depend entirely on the yolk for 

 nourishment. This type occurs in all the Buthidae (Buthus, 

 Parabuthus, Uroplectes, Centrums, Androctonus) which I 

 have examined, and also in Broteochactas, Bothriurus, Euscor- 

 pius, and Vejovis. It is probably the more primitive mode 

 of development, agreeing as it does in many respects with 

 other Arachnids. The egg of Vejovis is much smaller in 



* V. Brauer, Zeitschr. wiss. Zool. vol. lvii. ; Laurie, Quart. Journ. 

 Micr. Sei. vol. xxxi., &c. 



