ASCIDIACEA STOLONIC GEMMATION. 



457 



the separate individuals as small, rounded bodies, each provided with 

 a cavity. In individual cases a longer proliferating stolon seems to 

 occur, as in the stalked colony of Colella pedunculata, in which 

 HEBDMAN found that each individual gave off into the common stalk 

 a body-process (evidently the proliferating stolon). On this, then, 

 the young buds arise and detach themselves, shifting upward in the 

 common mantle-substance in proportion as they develop further. In 

 another form belonging to this group, described by KOWALEVSKY 

 as Didetnnum styliferum, but which, according to DELLA VALLE 

 (No. 68), belongs to the genus Distaplia, the small buds which early 

 become independent, arise, as KOWALEVSKY conjectured, on a process 



Frc. 230. Free-swimming larva of Distaplia (after DELLA VALLE). d, atrial cavity ; 

 e, atrial aperture ; en, eiulostyle ; lid, intestine ; i, branchial aperture ; k, detached 

 1'iid ; /'. hud in the act of dividing ; m, stomach ; n, ganglion ; oe. oesophagus ; s, 

 adhering or-;m ; .s7, stolon ; ./;, larval tail. 



directed posteriorly, which must evidently be regarded as a pro- 

 liferating stolon. This is also the case, according to LAHILLE (No. 

 38), with the individuals of Distaplia magnilarva, but DELLA VALLE 

 (N<. 68) assumes that these processes are merely mantle- vessels. 

 Tlu- special characteristic of the Distomidae is the early detachment 

 of the small buds within the still free-swimming larva (Fig. 230). The 

 large larvae of Distaplia magnilarva. in which, according to DELLA 

 VALLE, the organisation of the adult Ascidian is almost perfectly 

 attained while the animal swims about freely, also show, between the 

 endostyle and oesophagus, a short proliferating stolon (st), from which 

 small buds that multiply by division (, ') are abstricted. 



