EXPLANATION OF PLATES. 387 



Figure 7, the germinal mass at the stage shown in Plate XX, Fig. 5, drawn with 

 a Tolles -}?, oil immersion, a, ectoderm, b, endoderm. c, pharynx. /, pericardium. 

 n, germinal mass, y, body cavity. A, blood corpuscles and mesoderm cells. B, fol- 

 licle cells. 



Fig. 8, section through genital string at the root of a mature stolon. 



Fig. 9, section through mature stolon a short distance from root. These two 

 sections are from the same series as the figures in Plates V, VI, VII and VIII. 



Figure 10, a wheel-shaped cormus of Salpa chamissonis. 



PLATE XLII. 



SALPA HEXAGONA AND SALPA PINNATA. 

 (Tolles T^, homogeneous immersion.) 



Figure 1, part of the embryo of Salpa hexagona shown in Plate XI, Fig. 1, from 

 another section in the same series. 7, somatic layer of follicle. 8, visceral layer of 

 follicle. 9, blastomeres. 



Figure 2, part of the embryo of Salpa hexagona shown in Plate XI, Fig. 3, from 

 another section in the same series. 



Figure 3, part of the section of Salpa pinnata shown in Plate XII, Fig. 7. 



Fig. 4, part of the embryo of Salpa pinnata shown in Plate XIII, Fig. 7, but from 

 the next section. 



Figure 5, part of a section of Salpa pinnata, between 7 and 8 of Plate XIV. 



Figures (5, 7 and 8 are from an embryo of Salpa pinnata a little older than Plate 

 XIV, cut in the plane of cut D, page 31. g, median atrium, or cloaca. </", gill-slits. 

 c, pharynx, y, body cavity, o, gill. 7, somatic layer of follicle. 8, visceral layer 

 of follicle. 9, blastomeres. 



Figure 9, part of the section of Salpa pinnata shown in Plate XVI, Fig. 3. 

 a, ectoderm, b, epithelial lining of gill-slits, b', cells of epithelial capsule. </ IV , gill- 

 slit. A, mesoderm cells. 8, follicle cells in body cavity. X, follicle cells in cavity 

 of atrium. 



Figure 10, part of Plate XVII, Fig. 2. c, cavity of pharynx, q, rudiment of gut. 



Figure 11, ectodermal rudiment of an embryo of Salpa pinnata at the stage of cut 

 D, page 31. a, ectoderm, b', cells of epithelial capsule. 8, follicle cells. 15, body 

 cavity. 



PLATE XLI1I. 

 SALPA DEMOCRATICA AND SALPA RUNCINATA. 



Figure 1, part of a fully grown chain of Salpa democratica. 

 Figure 2, the aggregated form of Salpa runcinata. 



PLATE XLIV. 



Figure 1 , a section through the eleoblast of an embryo of Salpa hexagona at the 

 stage shown in Plate III, Fig. 4. 



Figures 2, 3 and 4, three horizontal sections through the placenta of an embryo 

 of Salpa pinnata at the stage shown in Plate XXXV. Fig. 2 is at the level of the 

 letters in in Plate XXXV ; Fig. 3, at the level of the letters ft/. 2 : and Fig. 4, at the 

 letter y". Fig. 5 is a portion of Fig. 3 more highly magnified. 



