endodermal.. During the month of August, 1895, I made an 

 attempt to discover the ori;^in of the stolon in Perophora. 

 Larvae were put into aquaria, through which water was kept 

 constantly flowing, and although they settled down and under- 

 went tiie metamorphosis, at the expiration of nearly four 

 weeks, not the trace of a stolon sprouted from them. VJhen 

 larvae were afterwards sectioned and studied, nothing like 

 an epicardium, such as occurs in Clavelina, was found. 



If then such a structure exists in the larvae of 

 Perophora , it must be formed at a very late period. As I 

 shall try to show further on, it is doubtful whether there is 

 a true epicardium. in the buds of this Ascidian, and it is 

 possible that it is also absent in the larvae. 



The further Developmen t of the Bud . 



At the time when the bud-rudiment begins to e- 

 longate, or very shortly after, the rudiments of several nev/ 

 structures are laid down. These are the (1) pericardium ; 

 (2) the peribra nchi al sacs; (3) the d_orsal tube ; (4) the gut ; 

 and (5) the ga nglio n. These do not all arise sim.ultaneously 

 and although the rudiment of the pericardium is the earliest 

 to appear, it will be necessary to describe the formation of 

 the peribranchial sacs first, in order to render intelligible 

 certain relations between these and other structures. 



Orige n and Dev elopment of _th_e Peribranchial Cavit y. 



All investigators agree in deriving the peribran- 

 -15- 



