I DEVELOPMENT 19 
Tornaria was described and named by Johannes Miiller, who 
regarded it as the larva of a Starfish, in spite of his intimate 
knowledge of the development of these animals. Its correct syste- 
matic position was first demonstrated by Metschnikoff in 1869. 
The larva agrees with many other pelagic forms in being 
excessively transparent. The form described by Spengel as 
T. grenacheri attains the remarkable length of 9 mm. (nearly 
2th inch). 
The full-grown larva is usually ovoid, and a complicated 
“longitudinal” band of cilia runs in several loops over its 
anterior two-thirds. In side view, part of the surface limited by 
the ciliated band appears like a T with a double outline, the cross 
piece being bent downwards on each side, so as to form an anchor- 
like curve, the middle of which is at the anterior pole of the 
larva. In Z. krohni, which occurs on our south coast, the 
ciliated band has a wavy course. In the West Indian larva ® 
shown in Fig. 8 A, the ciliated band is produced into numerous 
tentacles, which fringe the sides of the T-shaped areas or grooves 
of the surface. These grooves and the cilia which border them 
are used for conveying food to the mouth.* At the apex of the 
larva is a thickening (e) of the ectoderm, bearing two eye-spots. 
The main locomotor organ is a simple transverse band (c.7) of 
“membranellae,’ vibratile structures composed of fused cilia. 
The mouth (m), on the ventral side, leads into the oesophagus, 
and this into the stomach (s). The latter is separated by a 
marked constriction from the intestine, which opens by the 
anus (@) at the posterior pole. 
On the dorsal side is a pore, the “dorsal pore” (d.p.), which 
leads into a thin-walled sac ().c1) destined to become the pro- 
boscis-cavity of the adult. To the right of the dorsal pore les 
the pulsating “ heart,” which apparently becomes the pericardium 
of the adult. Bourne and Spengel regard it as a right proboscis- 
vavity. In the older larvae, the second and third body-cavities 
appear as paired thin-walled sacs in close contact with the 
hinder part of the stomach. The skin is very thin, and the 
five body-cavities do not nearly fill the space between it and the 
Cf. Spengel, Monogr. p. 363 f. 
Bourne, J. Mar. Biol. Ass. (N.S.), i. 1889-90, p. 63. 
This closely resembles 7’. grenachert, but see Willey, op. cit. p. 285. 
Haldeman, Johns Hopkins Univ. Circ. vi. No. 54, 1886, p. 45. 
co wo to = 
