SALPA DEVELOPMENT OF THE BUDS ON THE STOLON. 505 



tudinal tube to which the buds adhere laterally. The blood-vessels 

 running in this strand, and the entoderm-tube which persists within 

 it and connects the branchial sacs of the individuals, 

 are of importance for the nourishment of the buds. 

 'Hi is longitudinal strand may be called the remain* of 

 the stolon. Its position with relation to the buds 

 changes, as its points of attachment wander more and 

 more upward, ?>., toward the branchial aperture 

 of the individual (Fig. 275), while the individuals sink 

 downward on either side of it. This change of position 

 can be most distinctly traced in the ganglia. The 

 neural tube of the stolon originally lies above the 

 entoderm-tube as is seen in Fig. 264. The ganglia 

 derived from the neural tube must consequently seem 

 to lie in the median line above the entodermal con- 

 nective canals (see diagram, Fig. 268). When, later, 

 the buds .become marked off laterally, the ganglia sink 

 lower down, and come to lie at the sides of the con- 

 necting canals ; indeed, in the diagram (Fig. 268) 

 they appear alternately to cover the canals and to be 

 covered by them. Later, the ganglia and, with them, 

 the individuals, sink still farther down. 



The sinking down of the buds on either side of the remains of the 

 stolon solves a difficulty which apparently presents itself in connec- 

 tion with their rotation. In examining individual 5 in Fig. 271, 

 and still more in considering the diagram Fig. 273, it may occur to 

 the observer to wonder in what way the endostyle-fold which, in 

 individual 5, lies on the left side, passed over to the right, since it 

 appears separated from the right side of the body by the entoderm- 

 tube of the stolon. We have tried to make this process clear by the 

 diagrams given in Fig. 276. The connecting strand ab, which 

 represents the remains of the stolon, originally runs from the neural 

 side of each individual to the haemal side of the next (proximal) 

 individual. After rotation has taken place, these strands would 

 assume a zig-zag course, as indicated in Fig. 276 B. Later, as the 

 buds sink down, the connecting strands, which are already attached 

 near the anterior region of the body, shift further forward to a 

 position quite near the branchial aperture, whereas the endostyle- 

 folds, which remain unaffected by this change, do not extend so far 

 forward. There is therefore no obstacle in the way to prevent the 

 union of the connecting strands ; by this union these strands appear 



FIG. 274. 

 Diagram il- 

 lustrating 

 the course 

 of transverse 

 furrowing in 

 the stolon of 

 Salpa, seen 

 from above. 



