176 



NEMATHELMINTHES 



proboscis and the neck, or, when the latter is absent, of the pro- 

 boscis and the trunk, but it is interrupted by the ingrowth of a 

 thin ring of cuticle which reaches down to the muscular layers 

 (Fig. 94). All the spaces in the skin of the proboscis open ulti- 

 mately into a circular canal situated round its base ; on each side 

 the canal opens into a sac-like structure which extends through 

 the body-cavity towards the posterior end of the animal. These 

 two lateral diverticula are termed the lemnisci. They have 



Fig. 94. A longitudinal 

 section through the an- 

 terior end of Echinorhyn- 

 chus haeruca Rud. ( From 

 Hamann.) a, The probos- 

 cis not fully expanded ; 

 b, proboscis - sheath ; c, 

 retractor muscles of the 

 proboscis ; d, cerebral 

 ganglion ; e, retinaculum 

 enclosing a nerve ; /, one 

 of the retractors of the 

 sheath ; g, a lemniscus ; 

 h, one of the spaces in 

 the sub - cuticular tissue ; 

 i, longitudinal muscular 

 layer ; j, circular mus- 

 cular layer ; k, line of 

 division between the sub- 

 cuticular tissue of the 

 trunk and that of the pro- 

 boscis with the lemnisci. 



always attracted considerable attention from the workers at the 

 group, and numerous functions have from time to time been 

 attributed to them. They are more or less hollow, and their 

 walls consist of sub -cuticular tissue surrounded with a scanty 

 muscular coat ; they contain the same fluid as the lacunae of the 

 skin of the proboscis, with which they are placed in communi- 

 cation by means of the circular canal ; and it seems most prob- 

 able that, as Hamann 1 suggests, they act as reservoirs into 

 which the lacunar fluid retires when the proboscis is retracted, 



1 Jen. Zeitschr. Bd. xxv. 1891, p. 113. 



