BIGELOW: EARLY DEVELOPMENT OF LEPAS. 143 
EXPLANATION OF PLATES. 
The figures of Plates 1-10 were drawn from the eggs of Lepas anatifera, and 
those of Plates 11 and 12 from L. fascicularis. 
An Abbé camera lucida was in every case used in sketching the eggs. The 
figures of Plate 1, and Figures 57, 63-65, 74-77 were drawn at a magnification of 
about 220 diameters ; all others in Plates 1-10 at about 365 diameters. The fig- 
ures of Plates 11 and 12 are magnified about 210 diameters. 
All figures, except those of transverse sections, are so arranged that the posterior 
end of the embryo, or the more pointed end of the vitelline membrane, is directed 
toward the bottom of the Plate; in transverse sections the ventral side is toward 
the bottom. 
Double-headed arrows are used in some of the figures to connect two cells of 
common origin. 
The vitelline membrane has not been represented, except in Figures 1-17 and 
94-97. 
Figures 1-80 and 95-99 are oriented by the axis of the vitelline membrane; all 
others by the axis of the embryo. 
The small circles without stippling indicate the positions of the oil spherules in 
the yolk. Nuclei are distinguished by wavy lines, or by stippling, to represent 
chromosomes. 
In Plates 2 and 3 a pale yellowish buff tint has been used to represent the more 
finely granular and more “ protoplasmic ” portion of the egg and blastomeres. 
Plates 1, 4,11, and 12 have been printed without tint. To aid in quickly dis- 
tinguishing between the derivatives of quadrants a, b, and c, all the blastomeres 
of quadrant b in Figures 38-59, 61 are printed in stipple without tint, and in Figures 
60 and 65 (Plate 7) the same method of designation has been employed to indicate 
the cells (07-678) of this quadrant concerned in the formation of the secondary 
mesoblast. 
In Plates 5-10 the pale yellowish buff tint has been employed to indicate the 
blastomeres derived from quadrant d, the primary mesoblast (d5-2 and its descend- 
ants) being distinguished from the other derivatives by receiving a stippling in 
addition to the tint. In Plates 8-10 the tint has been restricted to d*! (entoblast) 
and its derivatives. 
