communicating with the branchial cavity. 'His description is 

 very obscure, however, and the only points to be noticed are, 

 that the dorsal tube, accordinr: to this author, is derived 

 from the endodermal vesicle, and that it gives rise to the 

 ganglion. 



Giard (6) and Delia 7a lie (3 and 4) v/ho studied the 

 bud-development in different species of Ascidians, contribu- 

 ted nothing of value concerning the nervous-system, but both 

 ascribe a common origin to the dorsal tube and ganglion. 



The viev/s of Seeliger (29) are very different from 

 the foregoing. According to hi:., the dorsal tube and gan- 

 glion in the buds of Clave lina arise from a common rudiment, 

 which is derived from mesodermal cells. This belief was not 

 based on direct observation, since he did not examine suffi- 

 ciently young stages, but was arrived at through theoretical 

 considerations. The great similarity between the individual 

 cells of the nerve-rudiment and the free mesodermal cells in 

 the body-cavity of the bud, Seeliger holds in good evidence 

 for the mesodermal origin of this structure. He furthermore 

 points out that the cells composing the ganglion of the lar- 

 va, would be carried off in the blood after the disintegra- 

 tion of that organ, ana give rise in the bud to some of the 

 mesodermal cells. The latter would therefore be "directe 

 Abkcmmlinge eines friihere gangliosen Organs", and it would be 

 but natural for them to resume the function which they had 

 once possessed. Van Beneden and Julin {33) in their work 

 on the development of the buds of Clavelina, state, that the 



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