380 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



shown by the numbered parallel lines. It will be seen that these sections are not 

 exactly horizontal, but that structures on the right of the middle plane are cut at a 

 higher level than those on the left. As the drawings are arranged on the plate, the 

 anterior or oral end is below. 



In this plate blue marks the follicle ; red, the cloaca of the chain-salpa and its 

 derivatives; yellow, the cavity of the placenta, which is, in its origin, part of the 

 body cavity of the chain-salpa ; purple, the body cavity of the embryo, and orange, 

 the blastomeres. (In Figs. 2, 3 and 5, the structures marked g, g' and g'" were colored 

 orange by mistake, as they are derivatives of the follicle and not of the blastomeres.) 



The positions of the various sections and the relations of the parts will be made 

 clear by a comparison between the figures in this plate and the cut B on page 29. 



PLATE XIII. 



HORIZONTAL SECTIONS THROUGH AN EMBRYO OF SALPA PINNATA, A LITTLE OLDER THAN 

 THE ONE SHOWN IN PLATE XII, AND OF NEARLY THE SAME AGE AS THE ONE SHOWN 

 IN PLATE XLI, FIG. 1. 



Figure 1 is the fifth section in the series; Fig. 2, the seventh ; Fig. 3, the twelfth ; 

 Fig. 4, the fourteenth; Fig. 5, the seventeenth; Fig. 6, the twenty-second; Fig. 7, the 

 twenty-seventh ; Fig. 8, the thirty-sixth, and Fig. 9, the forty-ninth. 



Cut C, on page 30, is a reconstruction, from this series, of a vertical transverse 

 section, and the planes of the actual sections which are figured in this plate are 

 shown by the numbered parallel lines. 



Blue indicates the follicle and its derivatives ; red, the cloaca of the chain-salpa 

 and its derivatives ; yellow, the body cavity of the chain-salpa and its derivatives ; 

 purple, the body cavity of the embryo, and orange, the blastomeres. 



The positions of the sections and the relations of parts will be understood by 

 comparison with cut C on page 30. 



PLATE XIV. 



HORIZONTAL SECTIONS THROUGH AN EMBRYO OF SALPA PINNATA, A LITTLE OLDER 

 THAN THE ONE SHOWN IN PLATE XIII, AND A LITTLE YOUNGER THAN THE ONE 

 SHOWN IN PLATE XXII. 



Figure 1 is the twelfth section in the series ; Fig. 2, the fifteenth ; Fig. 3, the 

 eighteenth; Fig. 4, the twenty-first; Fig. 5, the twenty-eighth; Fig. 6, the thirty- 

 fourth ; Fig. 7, the thirty-eighth ; Fig. 8, the forty-first, and Fig. 9, the forty-ninth. 



Cut D on page 31 is a reconstruction, from this series, of a vertical transverse sec- 

 tion, and the planes of the actual sections which are figured in the plate are shown 

 by the numbered parallel lines. 



Blue indicates the follicle and its derivatives ; red, the cloaca of the chain-salpa 

 and its derivatives ; yellow, the body cavity of the chain-salpa and its derivatives ; 

 purple, the body cavity of the embryo, and orange, the blastomeres. 



The positions of the sections and the relations of parts will be understood by com- 

 parison with cut D on page 31 . 



PLATE XV. 



A SERIES OF SECTIONS THROUGH A YOUNG STOLON OF SALPA PINNATA, IN A HORI- 

 ZONTAL PLANE, OR A PLANE PARALLEL TO THE LONG Axis OF THE STOLON, AND 

 TRANSVERSE TO THE BODIES OF THE CHAIN-SALP.E. 



Figure 1 of Plate V is a reconstruction which was made from a series of sections 

 at right angles to those in this plate, through a stolon at about the same stage of 

 development. 



