Kowalev/sky (12), for the buds of P erophora , was the 

 first to describe an endoder;r,al origin of thp nervous-system. 



According to him, the dorsal v/all of the branchial sac 

 evaginates to form a tube, v/hich retains its connection v;ith 

 the branchial cavity and v/hich he calls the "llervenrohr . " 

 In his later work on the budding of Ascidians (13) he des- 

 cribes the rudiment of the nervous-system in A maroucium and 

 Dideninum as "ein sehr langes, an vordern Ende zeiralich brei- 

 tes Rohr, dessen Lumen mit der Hohle des Kiemanseokes zu com- 

 municiren scheint" (I.e., page 455). He did not follov/ the 

 development of this tube, which he held to be derived from 

 the endodermal vesicle, and was ignorant of its relation to 

 the hyphophysis and nervous-system of the adult animal. It 

 is probable, however, that he sav/ the ganglion in Amaroucium 

 at least, but failed to recognize it, for he says (I.e., page 

 465), "Bemerkenswerth ist noch, dass iiber dem Nervenrohr sich 

 eine Anhaufung von sehr blassen Zellen befindet, welche bei 

 '•."•eiterer Entwicklung zu verschwinden scheinen." Amaroucium 

 is one of those Ascidians, in v/hich the ganglion lies above 

 the hypophyseal tube. 



Ganin (5), v;ho studied the bud-development in Pi- 

 demnum and Botryllus , derived the nervous-system from a ves- 

 icle which he described as being cut off from the inner ves- 

 icle of the bud, and converted into a long cylindrical tube 

 lying over the dorsal wall of the branchial sac. The gan- 

 glion, according to Ganin, becomes differentiated from a part 

 of this tube, the remainder of v/hich forms a ciliated organ 



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