18 HEMICHORDATA CHAP. 
name “ Eichelwurm ” used by German zoologists. But the idea 
expressed by Delle Chiaje was really a similarity between the 
collar of Balanoglossus and the outer shell of Balanus, the barnacle 
or “acorn-shell” found everywhere on rocks between tide-marks. 
e Fic. 8.— Metamorphosis of 
a Balanoglossus, probably 
: of Balanoglossus bimini- 
ensis Willey, Bahama 
Islands. All the figures 
are magnified to the same 
scale (x14). A, fully 
developed free-swimming 
larva, or TYornaria, side 
view ; B, commencement 
of metamorphosis, side 
view ; C, later stage, dor- 
sal view. Increase in size 
takes place after this 
stage ; a, anus ; b.c’, hody- 
cavity of proboscis; c, 
collar; 7, transverse 
ciliated ring ; d.p (in A), 
dorsal pore (= proboscis- 
pore), seen also in © on 
the left side, just behind 
the reference line p.c ; e, 
eyes and sensory thicken- 
ing of skin (in A); g, 
gill-pore ;  g.s, gill-sacs, 
developing as outgrowths 
of the alimentary canal ; 
three are already present 
in B, but are better seen 
in C, in which they are 
still without openings to 
the exterior ; 7, postoral 
part of the longitudinal 
band of cilia ; 7’, its prae- 
oral part; both 7 and JU’ 
are produced (in A) into 
tentacles, over which the 
band of cilia is looped ; 
the groove in the middle 
of the figure, between / 
and /’, conducts the food 
by the transverse groove 
to the mouth (m); p.e, 
blood-space of proboscis 
and pericardium (‘heart ” 
of larva); s, stomach. 
(After Morgan). 
Development.—The free-swimming, larval stage of Balano- 
glossus is known as Vornaria (Fig. 8, A). Several distinct forms 
of the larva are known,' although it is not yet possible to refer 
them with certainty to their respective adults. 
1 Spengel, Monogr. p. 370 f. 
