176 Gynandry in Arachnida 



of bisexuality ; that is, one side is male and the other female, with no atrophy or 

 distortion of parts except where mutual accommodation is necessary on the median 

 line. Naturally this disturbance of structure shows itself chiefly in the sexual region 

 of the epigaster. In the present instance the female side of the external genitalia 

 suffers less modification than the male side. In one particular, however, this indi- 

 vidual differs from all other bisexual spiders I have ever seen or heard of ; for while 

 the right side of the cephalothorax is male and the left female, in the case of the 

 abdomen the sexes are reversed — the right side being female and the left male. 



In view of the unusual character of this specimen I now supply 

 further details. 



The first two pairs of appendages of the cephalothorax, being uncon- 

 nected, retain their sexual characters undisturbed. Thus the right falx 

 (or mandible) is typically male — attenuate and divergent distally, with 

 four teeth on the forward border of the fang-groove, a proximal pair of 

 which the first is smallest of all and the second largest, and a distal pair 

 of intermediate size, the larger (the third) being slightly out of the line 

 of the rest on the side farthest from the fang-groove. The left falx is 

 typically female, equal in breadth to the right at the base, but wider at 

 the apex (i.e. not attenuate or divergent), with five fang-teeth, all in the 

 same line and equal, except the last, which is smaller than the rest. 



Similarly the right palp is typically male. In this particular specimen 

 the copulatory organs were nearly fully exserted at the time of capture 

 and are so shown in the figure. They are fully developed in every detail 

 without the slightest variation from the normal. The same may be said 

 of the left palp which is completely and perfectly female. 



As the cephalothorax differs in form and dimensions in the two sexes, 

 there is inevitably asymmetry of the carapace. In the first place the 

 clypeus of the male is rather higher than that of the female; conse- 

 quently there is in our gynandromorph a certain distortion of the ' face.' 

 The front row of eyes is straight but tilted upwards on the right (male) 

 side, on which side also the eyes are slightly nearer together and more 

 prominent. Another effect of the distortion is that the larger part of 

 the eye area falls to the left of the median line ; but it must be remem- 

 bered that part of this excess is normal, the eye area of a female being 

 slightly wider than that of a male. 



In the group of genera to which the present species belongs it is 

 usual for the occipital area (including the two posterior middle eyes or 

 not) of the male to be raised into a tuber varying in form according to 

 the species, limited on either side by a furrow or indentation or pit. In 

 several species this occipital tuber is so slightly developed as to be 

 scarcely perceptible, though the lateral grooves (called the post-ocular 



