104 F. II. STEWART. 



It is convenient in describing the animal to divide the body 

 according to the regions of the alimentary canal. I shall, 

 therefore, frequently refer to pharyngeal, oesophageal, intes- 

 tinal, rectal, and post-anal regions. The oesophageal region 

 it is convenient to divide into anterior oesophageal in front of 

 the nerve-ring, posterior oesophageal behind it. 



Habitat. — Oncholaimus vulgaris is very common 

 under stones between tide-marks. It is essentially a sociable 

 animal, twenty to thirty being often found together under one 

 stone ; it is not usual to find individuals isolated. 



The Cuticle. 



The cuticle forms a continuous layer over the whole body, 

 as in all Nematodes, and passes in through all the apertures, 

 mouth, anus, cloacal opening, and vulva to become continuous 

 with the cuticular linings of the cavities into which these 

 apertures open. 



It is a structureless membrane •00215 mm. thick, and with 

 certain stains shows a division into two layers (PI. 7, fig. 15). 

 Hairs occur in certain localities : (1) in a circle round the 

 head at the base of the lips ; (2) scattered over the anterior 

 oesophageal region, and (3) arranged along the mid-dorsal 

 and mid-ventral lines (PI. 7, figs. 1 and 2). They are more 

 abundant in the dorsal than in the ventral line, and in the 

 oesophageal than in other regions of the body. The numbers 

 vary considerably in difi'erent individuals, but an average 

 would give about forty for the dorsal and twenty for the 

 ventral line. In the female several occnr in front of and 

 behind the vulva. 



Each hair is formed by a projection of cuticle, while at the 

 base the cuticle is perforated by a minute canal containing a 

 core of protoplasm passing out from the epidermis. The hairs 

 along the median lines spring from the centre of shallow de- 

 pressions in the cuticle. 



The canals at the roots are, as pointed out by Jiigerskiold 

 (10), identical with the integumental pores of Bastiau (2). 



