APPENDICULARIA FLABELLUM. 



511 



a haemal flexure. In the middle of its h.-emal aspect the en- 

 doderm of the pharyngeal cavity is raised into a fold, which 

 projects into the blood-cavity contained between the endo- 



Fig. lil.—Appendicularia flabellvm. 



I. The entire auiuial, wiih the caudal appendage in its ordinary' position, or turned 

 forward. 



II. Side view of the body, with the caudal appendage forcibly bent backward. 



A, tlie body; B, the caudal appendage; a, oral aperture; b, the pharynx; c, an 

 atrial opening; d, tlie corresponding stigma, with its cilia ; e. anus; /, rectum ; 

 {7, oesophagus; h, ^, stomach ; k. testis; I, urochord ; m, cellular patch at the 

 side of the oral end of the body ; 7^ endostyle ; jj, yangiion ; q, ciliated sac; r, 

 otocyst ; s, posterior nerve with its ganglia, t ; en, eudoderm ; ec, ectoderm. 



derm and ectoderm. The walls of the bottom of the fold are 

 thicker than the rest, so that, viewed sideways, it has the 

 aspect of a hollow cylinder. This is the endostyle^ (Fig. 

 147, n.) 



^ So described and named in my " Observations upon the Anatomy and 

 Physiology of Salpa and Pyrosoma', together with Remarks upon Doliolum 

 and Appendicularia." ("Phil. Trans.," IftSl.) In 185(5, however, I stated: 

 " With regard to the endostyle, I have nothing important to add to my pre- 

 vious account, except that I 'believe it to be here, as in other Ascidians, the 

 optical expression of the thickened bottom of a fold or groove of the branchial 

 sac." ( Quarterly Journal of Microacnpical ScUnce, April, 1856.) In my memoir 

 on Pyrosoma ("Linn. Traiis.," 1800, p. 205), the endostyle is stated to be "in 



