the sane end is reached by entirely different roads, and in 

 the foi-mer organs do not proceed from corresponding organs, 

 or even their germ-layers, in the latter, and moreover, since 

 in the bud a rudiment derived from one and the sam.e larval 

 germ-layer may give rise to structures of widely different 

 nature, one is compelled to believe witn Hjort, that "die 

 Knospen der zusanmengesetzte Ascidien ein Entv/icklungsprocess 

 ist, in v/elchem sam.tliche Organe durch 'Neubildung' aus einer 



sehr primitive Anlage entstehen." "Die Knospe muss 



ihre eigenen Gesetze haben und muss, da sie aus einer wesent- 

 lich anderen Anlage hervorgeht als die Larve, auf andere 

 Weise gebildet werden. Ebenso wie dass Ei, m.uss das :iate- 

 rial, die Anlage, welche den Ausgangspunkt fur die Entwick- 

 lung bildet, als ganz undifferenzirt gedacht werden und muss 

 alles enthalten, was zur Bildung eines ganzen Individuimis no- 

 tig ist, ebenso wie die Blastula des Eies," (9:, page 225). 



The behaviour of the 'm.esooerm' in the bud-devel- 

 opment of Perophora viri dis is of much interest, ov/ing to the 

 number and variety of organs in whose formation nesodermal 

 cells are concerned. As we have seen these cells give rise 

 to the pericardium, the dorsal tube, the ganglion, and the 

 sexual organs; they also produce the musculature, and, as 

 Kowalewsky (14) and Seeliger (32) have shown in other Asci- 

 dians, in Perophora also they doubtless become the cells of 

 the cellulose test. 



I have spoken of the cells which go to form the 

 pericardium, nervous-system, etc., as 'mesoderm.al • , because 



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