:>^ 



DOL10LIDA. 



55 



20 - 



asexual and eight in the sexual forms, the anterior and posterior 

 of them acting as sphincters. A tailed larva is formed, and 

 develops into an asexual form which produces a budding stolon. 

 The buds are polymorphic, there being three kinds, one of which 

 alone becomes sexual. 



The asexual form (Fig. 46) presents the following features : 

 It has nine muscular rings, 

 and the ganglion is placed 

 behind the fourth. The 

 mouth is surrounded by ten 

 lobes, the atrium by twelve. 

 There is an otocyst (4) in 

 the body-wall on the left 

 side which contains an oto- 

 lith and in some species 

 opens to the exterior. The 

 body carries two median 

 appendages, a dorsal one 

 (cadophore), arising far back 

 near the atrial opening (19), 

 and a ventral one, the stolon 

 (8), arising behind the fifth 

 muscular band. The stolon 

 will be described below. 

 The dorsal process contains 

 a blood space divided into 

 two by a septum, and its 

 dorsal ectoderm is columnar. 



In the sexual form (Fig. 

 47) the mouth is surrounded 

 by twelve lobes, the atrial 

 aperture by ten ; there are 



eight muscular rings and the ganglion is placed behind the 

 third. There is no otocyst, both the stolon and dorsal appen- 

 dage are absent, and there is a greater number of stigmata. 

 There is an ovary and a testis, both unpaired ; they open a little 

 to the left of the middle line behind the anus. 



The ovary never contains more than one ripe egg at the same 

 time, but as soon as this is expelled a second is formed, and after 

 that a third. After the third egg is laid the ovary atrophies 



15 



19- 



16 



FIG. 46. Diagram of a longitudinal-vertical sec- 

 tion through the asexual (budding) form of 

 Doliolum (after Delage and Herouard). 

 1 mouth ; 2 peripharyngeal band ; 3 endostyle ; 

 4 otocyst ; 5 heart \6 left pharyngeal diverti- 

 culum ; 7 mesoderm ; 8 stolon ; 9 diverticulum 

 from left side of cloaca into stolon ; 10 aper- 

 ture of oesophagus ; 11 pyloric glands ; 12 sto- 

 mach ; 13 intestine ; 14 anus ; 15 nerve ; 16 tac- 

 tile process ; 17 exhalent aperture ; 19 dorsal 

 appendage ; 20 hinder wall of pharynx with 

 stigmata ; 21 subneural gland with the closely 

 adjacent ganglion ; 22 opening of duct of sub- 

 neural gland (dorsal tubercle). 



