4 ARKIV FÖR ZOOLOGI. BAND 6. N:0 2. 



its base. This projection is probably homologuous with the 

 socalled pseudocapitulum of RJiagidia a. o., but has, con- 

 trary to that, no sense hairs; at least I bave been unable to 

 see any even by an amplification of 812 X 1 ; on the upper side 

 of the cephalothorax there are two pairs of long, slender 

 tactile hairs, inserted in comparatively small pores. 



The anterior pair is slightly shorter than the posterior 

 one, inserted near the median line, half way between the 

 middle and the anterior margin, and points obliquely for- 

 wards and outwards. 



Fig. 1. 

 Fig. 1. Rostruni and cephalothorax ol S. formicorum, dorsal view. 



The posterior pair is inserted close behind the middle, 

 further laterally the anterior one, about halfway between the 

 median line and the sides. 



Besides the tactile hairs there are 3 pairs of very cha- 

 racteristie, rather stout, straight and densly plumose bristles 

 which are of even width throughout and blunt at the top. 



Of these the median pair is only a little more than half 

 as long as the other two wich are of equal length. Their 

 position is shown in textfig. 1. 



The eyes are very prominent and sphaerical. The swollen 

 portion behind the eyes scems to be a sense organ of some kind. 

 Tt is possible to discerne through the skin 3 — 4 Hght-refract- 

 ing bodies or crystals which recall statocysts. 



