No. 625] TlIK FA-OLVTIOX OF AHT lIllOl'ODS 145 



is represented by the Myzostoiiiida, whicli are regarded 

 by some authorities as occui)ying a position intermediate 

 between the oli<Ttopod Annelida and the Tardigrada. 



The position of the Tardigrada is still a subject of con- 

 siderable discussion, and the decision of the matter de- 

 pends largely upon the settling of the (piestion whether 

 the apparent simplicity of their organization is due to 

 the retention of a primitively simple condition, or to a 

 secondarily acquired simplicity brought about by reduc- 

 tion or degeneracy, etc. If the simi)licity of the Tardi- 

 grada is a primitive one, there is iniicli to be >;nd in fax or 

 of placing them next to the M \ /oMoinida lii the Mv zo- 

 stomida-Onycliophora grou]): hiil wlicilicr liic Lnmua- 

 tulida should also be included in this uroup seems very 

 doubtful. 



From the resemblance of the adults to Ei-io]->hyid mites, 

 and of the immature forms to such short-bodied mites as 

 Phytoptu.^, etc.. many recent anllioi'ities would i»lace the 

 Linguatulida near llic Acarina a iiiiiiily nioditicd ai-oup 

 far remov(Ml tVcm the ha^c of tlic artliro] .odan stem. If 

 this vi(.x\ i. ,M,Mc. 1. Ilic ai.paicni HinpliciiN ,)f t'lc Lin- 

 gnatnlida is \o Ur ivuar.lc.l a^ the result of a rcducti.tn or 

 dcuuicralion lathc. man the ictention m' a piimilivc 

 condition, in 1'...,,,^ la' M'Mio\,m1 t'loni the ha^- of the 

 aithropod.-n, Men: and i f 1 he .i ni] )lici t> ..f t he TarJ.iui adu 

 is primitive, wliih' that of the Lin-n:itnli(hi ha^ h.'cn mH'- 

 ondaiiK ac-iuiied tliiouuh ivdnctioii oi .h-cneiacx. the 

 apparent icMMnl lance hetueen the Taidi-a<ia and 

 Linun.atnlida muM he leuaided a^ the ir^nlt of conxer- 

 gence. Ol- p;ii;dle|i.m. lallur than o' .•nn-^aiiunlnily. 

 rndei- l!i(-e con.lition^ the Li ii-uatulida coiild not he 

 group,.,! uith tlu^ Tanliiiia.la. il ih. !att,.r aic p!:i,.,Ml 

 next to the M > /,.M ,>mi.la in lh,' \h /oMonii,la ( »n> clio 

 ])hora ui,)up: hnt if the aiMwMvnt ^ia'plicitx of th," Tanli 

 grada i^ aNo ,1m' to -vductn>n or .l,-i:,.nerac> . tlu^x too 



althouuh I'hi^ ,lo... not appear t,. h,' xei> pioh.-.lre f.oni 



