Classification of the Spiders. 321 



but an organ of quite a peculiar nature, and at the same time 

 brings along with it the presence of another organ, the cala* 

 mistruni." But notwithstanding this, and though it is bj no 

 means difficult to ascertain the presence or absence of the 

 organs in question, the difference in this respect has not, in 

 general, been considered a character of greater value than 

 those on which subfamilies and genera are founded. The 

 reason appears to be not only that of two in other respects 

 closelj allied species the one may possess, the other want the 

 cribellum and calamistrum, but also that the other parts of the 

 spinning-apparatus have been found to vary most materially 

 within very nearly allied groups of spiders. The number of 

 the spinners may in fact vary in the most extraordinary way. 

 Within the family Theraphosoidge {= T/ieraphosini, Auss.)j 

 which is characterized, among other things, by having only 

 four spinners, there is, however, as has been said above, one 

 genus, Hexathele, Auss., which has six spinners ; within the 

 genus Storena of the family Zodarioidai (one of the most 

 natural families m the whole order) there are not only species 

 with all the six spinners well developed, but others in which 

 the intermediate ones are rudimentary, or wanting, in one of 

 the sexes alone ; in some Zodarioidaj both sexes appear to be 

 destitute of the intermediate spinners. In most Zodarioidaa 

 the inferior spinners are much longer than the superior, in 

 others these four spinners are of about the same length ; 

 sometimes (not always) the two inferior ones are fixed on a 

 common basal part. In the Agalenoidm the superior spinners 

 are in general much longer than the inferior, and their second 

 joint provided with tubuli textorii along its whole underside ; 

 but in some cases the superior spinners are only of tlie same 

 length as, or shorter than, the inferior, and are provided with 

 tubuli textorii only at the apex; sometimes (Cj/bceus) their 

 second joint is rudimentary, &c. That the spiders which are 

 provided with cribellum and calamistrum do not form a natural 

 unit is admitted even by Bertkau {A, p. 386). Nor does 

 he deny that spiders belonging to the two different groups 

 Meromammillata and Cribellata may show an " outer resem- 

 blance" to each other — a)id it would indeed be difficult to 

 deny that Zora is like Zoropsis, or that Coelotes and Gybceus 

 resemble Amaurobius] but, says he, " this external resemblance 

 does not prove anything as to the natural affinity more than the 

 habitual resemblance of the shrew to the mice, or that of tiie 

 blind-worm or the eel to the serpents, &c." (Z?, p. 340) — ex- 

 pressions which appear to me strange, to say the least. Ur can 

 it really be Dr. Bertkuu's opinion that the jtresence or absence 

 of a cribellum and calamistrum is of the same systematic 



