Anatomy and Development of Scorpions. 131 



Fam. V. ButMdaB = Buthid£e, Sim.,+ Chcerilus. 



This family is characterized by a yolky &ggy apoikogenic 

 development, and the reticulate type ot" lung-book lamellae. 



Subfam. I. Cs^BiLiNi. 

 Chcerilus. 



Of this very peculiar genus I have only seen the Umg-books, 

 and it is with some misgivings that I place it here on account 

 of their structure. 



Subfam. 2. 5i7^Tjrziv/=Buthidae, Sim. 



[Prionurus], ButJius^ Parahutkus, {Orosphus)^ Butheolus, 

 {Archisometrus), [Isometroides] y Uroplectes^ (Titi/obuthus) , 

 [Pseudohuthus) , Isometrus^ Tityus^ Centrurus, [Heteroctenus) ^ 

 [Ananteris) y [Gharmus) ^ Heterocharmus^ {Stenochirus) . 



Looked at from the point of view of the evolution of the 

 order there is little doubt but that the apoikogenic type of 

 development is the most primitive. It is only one step from 

 the laying of the eggs, which is the almost universal custom 

 among Arthropoda. Pertpatus, Galeodes, some Diptera, and 

 some of the mites form exceptions to this habit, but in some 

 of them the internal development is evidently secondary. 

 Further, the eggs containing a considerable amount of yolk 

 are probably nearer the primitive type than those in which 

 the yolk is absent. This, indeed, is necessarily so if the 

 laying of the eggs was the primitive habit. This makes the 

 Chactidge, Bothriuridte, and Buthidse the more primitive 

 forms in these respects. 



Witli regard to the structure of the lung-books, I am in- 

 clined to consider the '' spinous " type as the original. The 

 reticulate type is more complicated, having pillars over part 

 of its surface and a network of ridges over the rest. The 

 " arcade " margin must have arisen from the " spinous " in 

 two or three separate sections, as it seems impossible to connect 

 EuscorpiuSy lurus, and Diplocentrus genetically to the exclu- 

 sion of the other forms. In this case we are left with 

 probably the Chactini as our starting-point, the highly 

 moditied sternum seeming to exclude the Bothriuridag. From 

 this would diverge four lines of descent — Buthidaj, Bothri- 

 uridse, Euscorpius, and luridae. The luridae, of wlrich the 

 Vejovini are the more primitive, lead to the katoikogenic 



