system in the Phasmidia as well as th* ventral gland of 

 marine forms without assuming either de-differentiation 

 of the protonephridial system or de novo formation 

 vrithin the Nematoda. Properly speaking, the various 

 nemic excretory systems have only one point in common, 

 namely that they open through a ventral pore. 



Von Linstow (1909) presented a classification of the 

 Nematoda, based on the excretory system, which has 

 considerable merit though it is in disrepute because the 

 original author incorrectly placed many forms. The 

 general outline may be summarized as follows 



I. Secernentes. Lateral canals emptying anteriorly 

 through a ventral pore; chords narrow and high. [Ascaris, 



Oxyuris, Oxysoma, Nematoxys, Heterakis, Strongylus, 

 Cucullavus, Dacvitis, Spiroxys, Rictularia, Cheiracanthus 

 (Gnathostoma) , Tropidocerca, Ancyracanthus] . 



II. Resorbentes. Lateral canals absent, excretory pore 

 absent; chords 1/6 periphery; esophagus and gut often 

 atrophied. Feeding by resorption through cuticle. 

 [Angiostoma (Rhabdias) . Eustrorigylus {Dioctophyma), 

 Hedruris, Dispharagus, Ichthyonema (Philometra), Fil- 

 ar ia]. 



III. Pleuromyarii. Muscles extending over lateral 

 lines; excretory system absent, male with one spicule. 

 [Hystrichus, Trichocephalus (Trichuris), Triehosoma 

 ( Trichonomoides) ] . 



M 



Fig. 112. DIAGRAMS OF NEMIC EXCRETORY SYSTEMS. 



A — Rhabditis dolichttra; B — Heterakis galli7iae ; C — Macraeis 

 viovhvstern ; D — Spirovoyra nffinr ; E — Vurvllanus heterorhrons : 

 F — Camallanus lacuslris : G — CamalUnius viirrorephalus ; H — Ascaris 

 lumbriroifles : •! — Rhabditis stroniiyloides : J — Metastrongylns elon- 

 ytitits ; K — Stron(jylus equitius ; L — Oesophagostomum deutatum ; 



M — Avoyicliiis inii'dbilis ; N — Anaplectus granulosus; O — Chroma- 

 dora qitfhlrilineii : P — PJianodermaj)Sis longisetae. E & F, After 

 Toerr.quist. 19.31. Goeteborgs Kungl. Vetensk. Vitterhets — Samb. 

 liandl. ■.. B.. v. 2 ( :', ) : 1-441. figs. 113. pis. 117. Remainder 

 original. 



126 



