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Transactions of the Society. 



last stage of their larval existence. If, therefore, the worm is 

 dicecious, copulation must take place during the larval stage ; but 

 the fact that no vulvar opening has been seen in the larval cuticle 

 is not in favour of this hypothesis. 



Crawley has described how oviposition begins during the 

 shedding of the last cuticle, and the old cuticle itself appears to 

 act as a protecting cocoon for some of the eggs. The remaining 

 eggs are probably deposited later in the soil. 



The following are the chief characters of the adult female : — 

 The largest specimen measured was 48 mm. in length and 

 • 6 mm. in thickness. The anterior end is somewhat more taper- 

 ing than the posterior, which is bluntly rounded. The cuticle at 

 the tip of the head is greatly thickened. Two pairs of small 

 cephalic papillae are present — one pair subdorsal, one subventral 

 (figs. 7 and 8, s.cl.p., s.v.p.) — the terminations of which are at the 



O-l rtvrn 



Fig. 9. — Mermis myrmecophila. Larva from Lasius flavus. Surface view of a 

 portion of the lateral field in a stained whole preparation. 



bases of shallow conical depressions in the cuticle. A pair of 

 structures which appear to be the " lateral organs " (figs. 7 and 8, /.) 

 are situated laterally in the position usually occupied by the third 

 pair of papillfe (which, on this interpretation, appear to be absent 

 in this species). These lateral organs have the form of simple, 

 deep, tubular pits in the cuticle, with a papilla-like conical 

 structure, doubtless carrying nerves, rising to meet them from tlie 

 subcuticular layer. (It is, of course, possible to interpret these 

 organs as lateral papillfe, their only difference from the other 

 papillae being the greater depth of the cuticular depression. In 

 this case the missing organs would be the "lateral organs" 

 which are said to be always present in other members of the 

 family.) The diameter of the head at the level of the papillae is 

 O'l mm. 



The oesophagus (figs. 7 and 8, ois.) is a long, sinuous, slender 



