REPORT ON THE CRINOIDEA. 



251 



in ihrer urspriinglichen Gestalt veranclerte Basalia." He supposed these basals to be in 



a more embryonic condition tlian those forming the rosette of Comatula, and still 



remaining independent of one another as five 



isolated j^lates. But if this be the case one 



would surely expect to find the basals 



below the radials, and separating them from 



the top stem-joint as in the early stages of 



the Pentacrinoid larva of Comatulge and in t t Vj^gg^M ''tMS^^ nMmms^-f>i 



the Stalked Crinoids generally. 



Ludwig, however, represents the supposed 

 basals both in horizontal and in vertical 

 sections as occupying a position above the 

 radials, and forming the floor of the body- ^ 



cavity some way above the chambered organ, 



with which the basals of Crinoids are always ■ . ^mi^- 



closely related. The position assigned by 

 him to the basals of Hhizocrinus is one which 

 I have no hesitation in describing as utterly 

 impossible for these plates to occupy ; and 

 the dotted line inserted in his longitudinal 

 section to mark the junction of the supposed 

 basals with the first radials below them is 

 purely imaginary. The same may be said 

 of the lines that indicate an enveloping of 

 the radials by upward processes of the 

 supposed top stem-segment below them, 

 which would cut off the radials altogether 



frnm tlip pytprinr of -f-hp palvsr ^pninmrp wnnil- ^"'- 17.— Diagrammatic vertical section through the calyx and 

 irom tne exterior OI ine CaiyX ^^COmpare WOOa- ^-^^^ ^j Rhlzocrinus h/otensis ,- x 75. Altered from Ludwig. 



+ fl 1 "tN T1io+ v>or.-f /-vf +V>q /^oIttxt /-.-P PTiiV/i The section is represented as passing through the middle line of 



cut, ng. Li ). 1 nat part 01 tne CaiyX 01 HIUM- ^ ray on the left hand side, and as almost (but not quite) iuter- 



1-1 • n 1 1 T 1 • J. radial on the right. A, axial cord of ray ; at, primary inter- 



CrinUS which was considered by Ludwig to radial cord ; b; basal tube ; *„ first brachial ; br, central 



1 ^ -111 1 • calcareous plug, the basal rosette of Sans ; ca, fibrillar sheath 



represent tne embryonic basals altered in round vascular axis of stem ; c/i, chambers of the qmnque- 



. , .... . nil locular organ ; ch' their downward extension into the stem; 



position, though not m nature, really belongs c.co., portion of circular commissure formed by the secondary 



./ o interradial cords ; fg, fore-gut ; G, mid-gut ; I, basiradial liga- 



tO the radials as was figured by SarS,^ who ment ; m, muscle ; nr, oral ring of the ambulacral nervous 



° *' system ; 0, oral plate ; Ri, radial ; re, rectum ; xl, top stcm- 



Spoke of these plates as follows: "etaut jilnt; T, tentacle ; i., central vessel of stem ;»/. nadial water- 



^ ■■- vessel ; v)r, water-vascular ring ; x, plcxiform glaua. 



tronquees dans leur partie interieure, elles 



forment reunies un large anneau en laissant entre elles au milieu un esj)ace arrondi 

 ou un peu pentagone, remph par la plaque ' en rosette ' (fig. 42, 43, r) mentionnee plus 

 haut, reste probable des basales. Au 2?oint oti cette plaque rencontre le bout tronque 



1 Crinoides vivants, p. 14. 



