Organ in a Spider. 231 
when their significance is protective they are equally well 
developed in both sexes, and appear at a very early age in 
the life-history of the individual *. 
Stridulating-organ in the male of Cambridgea antipodiana (White). 
Fig. 1.—Dorsal view of the organ and adjacent parts. a, posterior region 
of carapace ; 6, anterior region of abdomen; c¢, heart-shaped horny 
tooth ; d, cavity with arched ridges ; g, horny plate of pedicel. 
Fig. 2.—Partially diagrammatic side view of the organ and adjacent 
parts, the cavity with its arched ridges being represented as seen in 
section. Lettering as in fig. 1, with the addition of e, stigma of 
pulmonary sac, and f, muscular scars. 
Upon working through some of the spider material con- 
tained in the collection of the British Museum, I chanced 
* Tam not aware whether the stridulating-organs of the Theridiide 
and Linyphiide are present in immature members of the male sex or 
whether they are developed only at the period of the last moult, when 
sexual maturity is attained. If, as in the case of the Mygalomorphe, 
they are practically as perfect in the young as in the adult, it seems to 
me that the evidence of their being solely of a sexual function will be 
considerably weakened. But if, on the other hand, they appear, like 
typical sexual characters, either only just before or simultaneously with 
the attainment of maturity, there will, I think, be no reasonable grounds 
for doubting that they are exclusively of sexual significance. 
