Xo. 4S<)] 



POISOX GLAXDS 



503 



tory cells, so that there is no marked dinVrentiation into inland and 

 duet." 



The glands in Notunis and N'hilheodcs arc likcuisi^ invagina- 

 tions of the epidermis. Tluy are surrounded hy ;i slicaih of corium 

 pushed inward l)y the dc\ clopinu" i:ian(L A> sliowu in Fio;. 2, 

 d and /, the sheath is tliiinu'r and <l(Miscr than the nv^i ot' llic corium. 



is a layer of pigment cells ( Fig. 2, j). c. i wliicli is frc(|uciuly fouml 

 to extend about the gland hetwciMi the sheath and thi> i;lan(l ti>sue, 

 thus occupying the same relative position as in tiu^ skin. The 

 arrangement of the pigment layer in relation to the spine glands 

 shows that they are invaginated from near the tip of the spine. 

 Near the tip, the pigment layer (Fig. 5, p. c.) turns upon itself and 

 passes over the gland to its base, toward the root of the sj)ine. 

 Thus the glaitd 'is invested bv two lavers of pigment cells with 

 corium l)etween tliem (Fig. T), d). 'I'he ehivatc .rll> <.f the skin 



the two. The other rv\U .,f ,h' epidernu. a-^ ihc Ja-id i> ap- 

 proached, graduallv a.Muue an irregular diape. then bccnnun- 

 more elongated they a,v hnally tranMonn..! it, to th.- extremely 



toadfUh. hi the '^Uiwl^ of the hatter ilie e].id.M-n.a! character of 

 the c-lU i. harely io.t. Thu> the .Hme celU. uhich in the mad 



are perfech' diMincl in the -iaud> of the t.-adnd.. a.id proj.Ht into 

 the u'huid cavity. 



