Annals of the Transvaal Museum 
i5 
tinct variety, macrognathus, with elongated jaws, which, in the dentition, 
is not very different from hamata found in the Waterberg district; and 
again, either of the two latter forms can by slight modification be 
changed into bechuanica, as found at Serowe in the Bechuanaland pro- 
tectorate ; this by reduction of the two anterior teeth leads on to hostilis 
of the Transvaal and marshalli of Mashonaland, or by enlargement of 
the same teeth to junodi of the Zoutpansberg and Waterberg districts. 
The known facts seem to be easily interpreted as the results of continuous 
variation, but it is proper to add that a complete series of intermediates 
is unknown, and that, from the nature of the case, all possible variants 
of the dentition could be arranged within an apparently continuous 
series arbitrarily chosen. 
Other characters of systematic value, found amongst males, are the 
spines or bristles on the upper and outer surfaces of the chelicerae, and 
the tooth or keel which is often present on the dorsal edge of the mesial 
surface of the upper fang. These characters in particular species are 
often highly developed, and present the appearance of hypertrophied 
structures. The dorsal tooth of the fang of ferox, for example, is very 
markedly stronger than that of any other species. 
This hypertrophied appearance, which is also exhibited by the 
characters of the flagellum (cp. that of the cervina group) and of the 
dentition (cp. marshalli) in various species, seems to suggest that varia- 
tion, either continuous or discontinuous, has proceeded uncontrolled 
beyond the limits actually required by the creature for the maintenance 
of its race. That is to say, it seems improbable that natural selection 
can have been the sole guiding factor in directing the course of variation. 
Unfortunately, this view cannot be checked by an adequate body of 
facts based on acquaintance with the mode of life of the various species. 
The function of the flagellum itself is unknown: it is not a weapon of 
offence or defence, and according to Heymons’ account of the breeding 
habits in Galeodes, is not employed during the mating process. Never- 
theless, Sorensen believes that the flagellum is eminently adapted to the 
function of handling spermatophores and states emphatically: “Le 
flagellum est l’organe copulateur des Solifuges.” At present, this is un- 
supported by observations on the living animal, and to me the hypo- 
thesis seems improbable in view of the extraordinary diversity in form 
presented by the shaft and the complete absence of the flagellum in some 
genera 1 . 
1 See also R. I. Pocock in A Monograph of the Terrestrial Carboniferous Arachnida 
of Great Britain, 1911, p. 2: “An important factor in the evolution of terrestrial 
Arachnida has been, in my opinion, a change from the method of pairing, as practised 
by Scorpions, to new and special methods, resulting in the modification of a part of 
one of the prothoracic limbs into an intromittent organ, often of great complexity. 
This may be seen in the Araneae, where the palps are modified, in the Solifugae, where 
the mandibles are modified, in some of the Acari, and lastly in the Ricinulei, where 
the legs of the third pair are modified. Even the Opiliones possess very special 
secondary reproductive organs.” 
In the Cambridge edition of the Encyclopaedia Britannica the account of Arachnida 
by E. Ray Lankester includes the following : “ ? intromittent organ of male (solifuge) 
lodged on the dorsal side of the first pair of prosomatic appendages.” 
