376 



JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



12, Blood corpuscles. 



13, Pole-cell. 



14, Spermatozoon. 



15, Follicular cavity, or 



body cavity of em- 

 bryo. 



16, Blastopore. 



17, Caudal region of em- 



bryo. 



18, Caudal nerve. 



19, Notochord. 



20, Embryonic mesoderm. 



21, Outer layer of brood 



sac. 



22, Inner layer of brood 



sac. 



23, Supporting ring of pla- 



centa. 



24, "Blood bud." 



25, Brood chamber. 



26, Degenerating area of 



follicle. 



27 and 28, Right and left 

 tubes of the pharynx 

 of the aggregated 

 salpa. 



29, Migrating placenta 



cells. 



30, Caudal nerve. 



31, Side walls of placenta. 

 33, Intercellular substance 



or supporting layer. 



PLATE I. 

 1, 2, 3, 5 AND 6, SALPA PINNATA ; 4 AND 7, SALPA CHAMISSONIS. 



All the figures are twice the natural size. 



Figure 1 , dorsal view of a fully grown specimen of the aggregated form of Salpa 

 pinnata. 



Figure 2, a young wheel-shaped cormus of Salpa pinnata, consisting of nine salpae. 



Figure 3, the same seen from the left side. 



Figure 4, dorsal view of a fully grown specimen of the solitary form of Salpa 

 chamissonis. 



Figure 5, dorsal view of a fully grown specimen of the solitary form of Salpa 

 pinnata. 



Figure 6, ventral view of same. 



Figure 7, ventral view of a fully grown specimen of the solitary form of Salpa 

 chamissonis. 



PLATE II. 

 SALPA DEMOCRATICA. 



Dorsal view of a fully grown specimen of the solitary form of Salpa democratica, 

 magnified about twenty diameters. 



PLATE III. 



1 AND 4, SALPA HEXAGONA ; 2 AND 3, SALPA CORDIFORMIS ; 5, 6 AND 7, SALPA 



CYLINDRICA. 



Figure 1, dorsal view of the aggregated Salpa hexagona, magnified five diam- 

 eters. 



Figure 2, left side of a young free specimen of the aggregated form of Salpa 

 cordiformis, magnified five diameters. 



Figure 3, dorsal view of same. 



Figure 4, an advanced embryo of Salpa hexagona, magnified twenty diameters. 



Figure 5, dorsal view of the solitary form of Salpa cylindrica, magnified four 

 diameters. 



Figure 6, dorsal view of a mature specimen of the aggregated form of Salpa 

 cylindrica, magnified four diameters. 



Figure 7, ventral view of the solitary form of Salpa cylindrica, magnified four 

 diameters. 



