312 Mr. E. I. Pocock on Liphistius and its 



to Thorell's Dipneumones + Hypochilusy and it may accord- 

 ingly be divided into Umbellitelarias, Cavitelarise, Pseudo- 

 territelaria^, Tubitelarise, &c. I am inclined, however, at 

 present to follow Dr. Marx in considering that the peculiari- 

 ties of the Pholcidge are sufficient to justify Dahl in the 

 establishment of a special tribe, Plagitelarige, for the reception 

 of this family. Furthermore I do not consider that the 

 presence of the C7Hbellum and calamistrum is necessarily an 

 indication of affinity between two or more families, even when 

 they belong to the same tribe. I even doubt if the presence 

 of these organs is sufficiently important to form a basis upon 

 which to establish families, and therefore a fortiori I cannot 

 agree with Mons. Simon in dividing the Arachnomorphie into 

 Cribellatse and Ecribellataj. 



This view as to the value of the crihellumf however, requires 

 some justification in the face of the great importance that is 

 attached to it by such eminent arachnologists as Mons. Simon 

 and Dr. Bertkau. 



It must be admitted on all hands that the value of this 

 character depends upon our knowledge of its origin. The 

 cribellum and calamistrum are found in certain families which 

 differ widely in other respects in structure and habits. Its 

 presence in these families may be accounted for, firstly, on 

 the hypothesis that they represent a natural group which has 

 evolved itself in a line parallel to the ecribellate spiders, the 

 two groups independently acquiring a similarity in form and 

 instincts ; secondly, on the hypothesis that the cribellum has 

 been independently developed in many of the families that 

 possess it ] thirdly, on the hypothesis that the ancestor of 

 existing spiders was cribellate, and that only a few of the 

 families in the course of their evolution have retained the 

 organs in question. 



The second of these possible explanations seems extremely 

 improbable, and is adopted by no one, so far as I am aware. 

 The classifications, however, of Bertkau and Simon imply a 

 belief in the first. Thorell, on the contrary, accepts the 

 last, although he has not produced a large stock of evidence 

 to support it. Nevertheless that he is right in his opinion I 

 do not doubt, although at the same time I fear that our views 

 are diametrically opposed on the subject of the ancestry of 

 spiders. He does not believe in the descent of these animals 

 from forms allied to the Pedipalpi, and he considers that the 

 resemblances between Liphistius and Phrynus are merely 

 analogous. I, on the contrary, think that there is a mass of 

 evidence, based upon anatomical and embryological grounds, 

 pointing to the conclusion that the Araueaj are the descen- 



