VERTEBilATION OF THE TAIL OK APPENDICULAR!^. 389 

 I 



Fig. 2. — Appendicularia {Fritillarid) furcata. Diagrammatic views of 

 internal organs, a. Diagrammatic vertical longitudinal section of the 

 *' body " of Fritillana furcata. The " tail " is not supposed to be cut, 

 but is drawn as a transparent object, b. A similar drawing of a 

 horizontal longitudinal section, the tail not being represented. 



The italic letters have the following significance in all five drawings :— 

 a. The auditory vesicle or otocyst. b. The olfactory pit. In contiguity 

 to a and b is the oblong anterior ganglionic mass of the nervous axis. 



c. The hood formed by a broad process of the dorsal integument. 



d. The tubular nervous cord or axis, where it passes from the anterior 

 to the posterior ganglionic mass ou the right side of alimentary canal. 



e. Stomach. /. Ovary, g. Testis, h. Notochord (urochord). i. The 

 tubular nervous axis in the caudal region, lying to the left side of the 

 notochord and exhibiting seven slight enlargements, which, excepting 

 the anterior (posterior ganglionic mass), are devoid of nerve-gangliot 

 cells, k. Fifth muscular segment or myomere of the tail. /. Anus to 

 the right of the median line, on the ventral surface, m. Heart, con- 

 sisting of two cells only, united by fibres, n. Right and left branchial 

 slit (a pair of circular ciliated orifices leading from the pharynx to the ex- 

 ternal surface). 0. The endostyle or glandular groove, ja. The mouth. 



