328 



BULLETIN OF THE 

 Fig. 27. 



Very young stolon : b, outer tunic ; c, wall of pericardium ; r, heart ; 1, sinus cavity ; 2, central 

 tube of stolon ; 3, cavity of central tube ; 4, constrictions iu outer wall of stolon ; y, y, ovaries. 



At about this period a long club-shaped mass of protoplasm 

 (Figs. 27 and 28, y) appears within each of the sinus chambers of 

 the tube; and soon after the constrictions (4) make their appear- 

 ance upon the outer wall. We now have all the parts which are 

 to take part in the development of the chain, and it will be best to 

 state here the future history of each, and to give an outline of the 

 development, before entering into the details. 



The wall of the outer tube, which, as we have seen, is part of the 

 outer tunic of the solitary form, is destined to form the outer tunics 



Fig. 28. 



Proximal portion of stolon a little more advanced, and rotated 90° from the position represented 

 in Fig. 27 : 6, c, r, y, 1, 2, and 4 as in Fig. 27 ; 3, thickened edges of inner tube ; s, germina- 

 tive vesicles. 



