46 Cobb — Nematodes, mostly Australian and Fijian. 



no very marked contrast with the spear as presented in other groups in the genus. 

 The parts accessory to the spear may conveniently be arranged in two groups, (1) 

 those serving to guide the spear in its forward and backward movements, and (2) 

 those which Hne the hps and forward part of the pharynx, and serving, in my opinion, 

 to give the animal a firm grip during the operations of piercing and sucking by which 

 it gains its living. The principal part serving to guide the spear is a chitinous collar 

 which is doubtless a further development of various similar but more simple contri- 

 vances found in all nematodes with a pharyngeal spear. In the present ease this 

 collar, which, were it not somewhat too flat, might be called bell-shaped, closely 

 surrounds the spear at the base of the pharynx, being firmly held in place by horny 

 processes anterior to it and partly constituting the interior wall of the pharynx. The 

 parts, lining the lips, and no doubt, as above stated, serving as biting organs, are less 

 easily described. In the first place it is necessary to note that the lips and the lip- 

 region are constructed externally much as in other Dorylaimi: there are six somewhat 

 confluent lips each bearing two papillae, the lip-region being expanded and the 

 papillae being arranged in two circles of six each, one circle inside the other but both 

 situated near the margin of the head. Inside these lips and extending backward some 

 httle distance further is the pharynx, which is, roughly speaking, pyriform in shape, 

 with the wider part foremost. Round the mouth-opening are ranged a number 

 of processes, probably six, one from each lip, which appear to be capable of radial 

 movement. Opposite the inner and anterior row of labial papillae a row of numerous 

 longitudinal ribs encircles the anterior part of the pharynx. The base of these 

 ribs or teeth is a transverse ring larger than any other of its kind found in the head. 

 What appears to be a repetition of this structure on a smaller scale and without the 

 transverse ring occurs' slightly further back, that is half-way between the mouth- 

 opening and the spear-guide. The object of these complex structures is open only to 

 conjecture, but I have httle doubt that they are used as biting organs, or possibly as 

 rasping surfaces in tearing down the cells of plants; I do not consider them organs of 

 mastication. The examination of these mouth-parts and a comparison of them with 

 those of Onyx, Mononchus and Oncholaimus, has convinced me that we have good 

 ground for regarding the spear-bearing genera and what I may call the tooth-bearing 

 genera (represented by Mononchus, Oncholaimus and other genera with a distinct 

 dorsal 'tooth) as being related to each other and perhaps constituting a grand group. 

 The further specific characters of D. labyrinthostoma are as follows : cuticle thick, 

 destitute of mg-rkings and hairs; neck cylindrical posteriorly, convex-conoid anteriorly; 

 head truncate; lateral organs not seen; eyes none; nerve-ring oblique; oesophagus 

 anteriorly one-fourth as wide as the neck but widening gradually and becoming, 

 near the middle, two-thirds as wide as the neck and so continuing to the end, where it 

 is separated from the intestine by a distinct constriction ; intestine three-fourths as 

 wide as the body, its. distinct pre-rectal part being twice as long as the body is wide; 



