128 A. H. L. NEWSTEAD. 



EXPLANATION OF PLATE 8, 



Illustrating Mr. A. H. L. Newstead's paper " On the Peri- 

 visceral Cavity of Ciona/' 



Explanation of Figures. 



at. Atrial cavity, b. Blastocoele. end. Endostyle. ep. Epicardiac tube. 

 g. Generative organ, h. Heart, i. Intestine, m. Mesentery attaching the 

 pericardium to the posterior end of the pharynx, o. Openings from the peri- 

 visceral cavity into the pharynx, pc. Pericardium, p. g. Posterior groove 

 of pharynx, fh. Pharynx, pv. c. Perivisceral cavity, s. Septum between 

 the perivisceral cavity and the atrial cavity, st. Stomach, v. Blood-vessels. 

 X. Artificial space (in Fig. 6). 



Fig. 1. — Transverse section of a small adult individual of Ciona through 

 the posterior end of the pharynx (1 in. obj.). 



Fig. 2. — Portion of the same section further magnified (i in. obj.). 



Figs. 3 — 5. — Three transverse sections of a recently fixed larva, Fig. 3 

 being the most anterior (i in. obj.). 



Fig. 6. — Transverse section of a larva at a more advanced stage of meta- 

 morphosis, showing the formation of the heart (\ in. obj). 



