496 



TUNICATA. 



m the other Tunicate* as the entodermal, endostylic, or epicardia] 

 process. Between the ectoderm and the entoderm of the stolon the 

 primary body-cavity extends, being directly connected with that of 

 the parent. In it we find an accumulation of mesoderm-cells (m) 

 completely enveloping the entoderm-process ; these, accordino- to 

 Seeligee, are produced by the simple immigration of mesenchyme- 

 cells from the parent. Such cells (mz) are found in large numbers 

 at the point of origin of the stolon in the neighbourhood of the 

 elaeoblast-tissue. 



While Seeliger considers that the mesoderm of the stolon results from 

 the immigration of a l arge number of mesenchyme-cells, Todaro (No 107) 

 regards it as arising from the division of certain large germ-cells (germoblasts 

 derived from the placental membrane (membrana germoblastoca, p 435) at 



em. 



tm. 



bfei M ' neuraltube ; "• "PP- Mood-sinus; „,.„,„,,„, rudiment?* W 



the cleavage of the original egg which gave rise to the solitary form Since 

 according to Todaro, the whole bud is derived exclusively from the descend 

 ants of these cells, the ectoderm and entoderm of the stolon taking no part in 

 the formation of the buds, these latter are to be traced back to a form of 

 sexual reproduction. Todaro regarded the buds (in Salpa-chains) as younger 

 members of the generation to which the solitary form belongs. 



Transverse sections through older stolons (Fig. 264) reveal a condi- 

 tion deviating somewhat from that above described, but showing 

 great agreement with the stolon of Pyromma (Fig. 257 p 490) In 

 the primary body-cavity, four regularly-arranged strands have 

 appeared. The uppermost of these, which we will call the neural 

 strand or newal tube (Fig. 264, n) contains a distinct lumen The 

 paired lateral strands also (c) are said by authors to have Iumina 



