No. 3.] GROWTH AND METAMORPHOSIS OF TORN ART A. 429 



are so unique that I have added three figures, 10, 11, 12, to PI. 

 XXIV. to show the course of the bands. A view of the apical 

 plate of the larva is shown in Fig. 10. The figure is placed in 

 a corresponding position to Fig. 7 for comparison with the apical 

 plate of the New England Tornaria. The longitudinal ciliated 

 band of the Nassau larva is drawn out into tentacle-like process 

 hanging freely, like a fringe, from the surface of the larva. The 

 ciliated band runs up along one side of a tentacle round its free 

 end and down the opposite side ; it then crosses over to follow 

 the same course on the next tentacle of the series. Besides the 

 four bands corresponding to those of Fig. 7, the apical plate 

 of the Nassau larva is further complicated by the presence of 

 other bands. These arise by the edges of the anterior lateral 

 and posterior lateral folds being drawn upwards nearer to the 

 apical plate. Thus if the parts b and b 1 of Fig. 6 were drawn 

 upwards towards the apical plate, they would form the bands 

 shown by b and b 1 of Fig. 10. These bands in the Nassau 

 larva are also drawn out into a series of tentacles. In this way 

 the apical plate of the larva has secondarily acquired a most 

 marked radial symmetry, as seen in the figure. The centre of 

 the apical plate itself contains a small more opaque spot which 

 contains the eyes. In the centre of this is a smaller, lighter 

 area. Running across the plate from right to left is a deep 

 groove. This groove is bounded at its sides by four narrow 

 ciliated bands which are not drawn out into tentacles, and which at 

 the ends of the groove become each continuous with four ciliated 

 bands, and these latter, at first not tentacular, soon become so. 

 Moreover, the four ciliated bands bounding the edge of the 

 grooves do not quite meet across the middle line, but end in 

 four points before reaching the eye spots. The arrangement is 

 thus seen to be identical with the apical plate of the New 

 England form. The extra-oral area in the middle line has over 

 its surface curious clear spots, as seen in the figure, each 

 bounded by a halo of pigment. Sections show these clear areas 

 to be large cells much like those found in the pigment bands of 

 the New England Tornaria. In the field posterior to the eyes 

 there is seen a faint furrow in the outer posterior line. The 

 circumoral area between the ciliated bands is very clear and 

 pushes in below the general surface of the larva. In the living 

 animal the tentacular areas are much nearer together than 



