372 



THE ORIGIN OF VERTEBRATES 



evidence as to their function is entirely wanting. With respect to the 

 pectens of the scorpion (Fig. 151), it has been suggested that they 

 are of the nature of copulatory organs, a suggestion which may be 

 dismissed without hesitation, for they are not constructed after the 

 fashion of claspers, but are simply elaborate sense-organs, and, as 



such, are found equally in male or female. 

 The only observer who has hitherto 

 specially studied the structure of the 

 sense-organs in the pecten is, as far as 

 I know, Gaubert, and he describes their 

 structure together with that of the sense- 

 organs of the racquets of Galeodes, in 

 connection with the lyriform organs of 

 arachnids, as though he recognized a 

 family resemblance between the three 

 sets of organs. 



The pecten of the scorpions is an 

 elaborate sense-organ, or rather group of 

 sense-organs, the special organ being 

 developed on each tooth of the comb ; 

 its surface, which is frequently flattened, 

 being directed backwards and inwards, 

 when the axis of the pecten is horizontal 

 at right angles to the length of the body. 

 The surface view of this part of the tooth 

 resembles that of the branchial organs or 

 of the llabellum in Limulus, in that it 

 is thickly covered with circular patches, 

 in the centre of which an ill-defined 

 appearance as of a fine pore is seen. In Fig. 152, B, I give a sketch 

 of the surface view of a part of the organ. 



Transverse sections of a tooth of the comb of Scorpio Europceus 

 present the appearance given in Fig. 152, A, and show that each 

 of these circular patches is the surface-view of a goblet-shaped 

 chitinous organ, Fig. 152, C, from the centre of which a short, some- 

 what cylindrical chitinous spike projects. Within this spike, and 

 running through the goblet into the subjacent tissue, is a fine 

 tubule. The series of goblets gives rise to the appearance of the 

 circular plaques on the surface-view, while the spike with its tubule 



Fig. 151. — Under Surface of 

 scorfion (androctonus}. 



The operculum is marked out 

 with dots, aud on each side 

 of it is seeu one of the pec- 

 tens. 



