384 JOHNS HOPKINS UNIVEESITY MORPHOLOGICAL MONOGRAPHS. 



Figures 5 to 10 of Plate XXIII are horizontal longitudinal sections of a stolon of 

 Salpa pinnata, at a stage a little later than Plate XXXIV, Figs. 8, 9, 10 and 11. Fig. 

 5 is the second section in the series ; 6, the thirty-third ; 7, the thirty-seventh ; 8, the 

 right half; 9, the left half of the fortieth, and 10, the forty-fourth. 



PLATES XXV TO XXXI. 

 SALPA PINNATA. 



A series of sections, longitudinal to the stolon and transverse to the bodies of the 

 salpse, showing the structure and the anatomical relations of eight salpse at succes- 

 sive stages of development. The capital letters mark the same salpse in successive 

 sections, and the letters with an accent mark their left sides. 



In all the figures the right side of the stolon is on the right side of the plate, and 

 as the top of the figure is distal the upper salpa in each figure is oldest. As the body 

 of an old salpa is longer than that of a young one, it is of course cut by more sections, 

 and is shown in more figures. The structure which is marked g in Plate XXV, Fig. 

 4, H; Fig. 7, E and F ; Plate XXVI, Fig. 1, F, and Plate XXVII, Fig. 2, C, is the 

 digestive tract, and not the right perithoracic vesicle, which is marked g in the other 

 figures. 



PLATE XXV. 



Figure 1 is the second section in the series ; 2 is the third ; 3, the fourth ; 4, the 

 sixth r 5, the seventh ; 6, the eighth, and 7, the tenth. 



PLATE XXVI. 

 Figure 1 is the eleventh section in the series ; 2, the twelfth, and 3, the fourteenth. 



PLATE XXVII. 



Figure 1 is the fifteenth section of the series ; Fig. 2, the sixteenth, and Fig. 3, 

 the seventeenth. 



PLATE XXVIII. 



Figure 1 is the nineteenth section in the series, and Fig. 2, the twentieth. 



PLATE XXIX. 



Figure 1 is the twenty-first section in the series ; Fig. 2 is the twenty -third ; Fig. 

 3 is the right half of salpa, B-B' ' , in section twenty-five ; Fig. 4 is the same in section 

 twenty-seven ; Fig. 5 is the same in section twenty-eight ; Fig. 6 is the same in sec- 

 tion twenty-ninth ; Fig. 7 is the left half of the B-B' in section twenty -seven, and 

 Fig. 8 is the same in section twenty-nine. 



PLATE XXX. 



Figure 1 is the thirtieth section in the series ; 2 is the thirty-seventh, and Fig. 3, 

 the forty-second. 



PLATE XXXI. 



Figure 1 is the forty-ninth section in the series ; 2 is the sixtieth, and 3, the sixty- 

 fifth. 



Figures 4, 5, 6, 7 and 8 are sections through the genital rod of a stolon a little older 

 than the one which is shown in Plate XLI, Fig. 6. 



Figure 9 is from a young stolon which had traces of constriction of the ectoderm 

 at its tip. 



