322 Prof. T. Tliorell on Dr. Bertkau's 



importance as the radical differences in the anatomy, and even 

 in the external appearance, that exist between a fish and a 

 reptile, between the eel and the serpent? To me it seems 

 impossible to prove that the presence of the spinning-organs 

 in qnestion is a surer indication of affinity in those spiders 

 which possess them tlian are most other structural features, 

 anatomical or external. Rather the reverse might be supposed 

 to be the case, from the fact that it is only the adult female 

 and the young of both sexes of the Cribellata that are pro- 

 vided with tlie cribellum and calamistrum, whereas in the aduU 

 males these organs are rudimentary or totally wanting. The 

 cause of this dissimilarity is of course this, that the adult 

 males have no need of the apparatus in question, as they do 

 not construct a web. And this again appears to me to prove 

 that the cribellum and calamistrum are organs that have origi- 

 nally belonged to the order of Spiders in general, and have 

 in the course of time been reduced and lost in a part of them, 

 those namely which no longer wanted them ; and this quite 

 independently of their greater or less affinity. Thus it is easy 

 to understand why we find these organs still in existence in 

 spiders belonging to very dissimilar groups, and also why 

 they are always wanting in those spiders which lead a roving 

 life and make no webs. The possibility of explaining, on 

 this hypothesis,the presence of the cribellum and calamistrum in 

 spiders which in all other particulars are widely different from 

 each other has not escaped Bertkau, " The systematic 

 significance of the above-mentioned organs," says he, " might 

 only be doubted in case that all spiders had possessed this 

 fourth pair of spinnerets, but had, with the exception of some 

 few genera, lost them in the course of time" [B, p. 339). 

 But he does not show why this cunnot be the case, nor does 

 he say anything more on the subject. 



For my part, then, I cannot acknowledge in Bertkau's 

 Cribellata and Meromammillata two natural or systematic 

 units ; but I think that these denominations may, nevertheless, 

 be of practical utility for designating the spiders in which the 

 cribellum (and calamistrum) is present or is wanting. It 

 would perhaps be better, however, to call them (Araneaj) 

 Cribellatoi and Ecribellatce — the Cribellata possessing jointed 

 spinners, or being "meromammillata"* quite as much as the 

 other spiders. As to the families into which Bertkau has 

 divided his Cribellata, some of them are no doubt so closely 

 related to certain ecribellate families, that they could well be 

 united with them. But on the ground of the modern, more and 



* I suppose, in fact, that tlie word Meromammillata is formed of fitpoSf 

 part (joint), and mavimilla. The term J^criheUatcc is formed iu analogy 

 with clapidatus, exoneraftis, (S;c. Compare also Evertehrata and Vertehrata, 



