PLATE II. 



Explanation of the letters used in the Plates. 



al Alimentary canal. 

 an Anus. 



Ac' Body -cavity of prseoral lobe. 

 be' Body-cavity of second region. 

 6c' Body-cavity of trunk. 



bp Branchial plumes. 



bt Basement-tissue. 



eb Ciliated Iiypodermic organ. 

 cm Circular muscular coat. 

 cos Peculiar ciliated folds (sensory ?). 



(jbs Glandular organ at posterior end. 



hp Hypoderm. 



int Intestine. 



Im Longitudinal muscular fibres. 



Ipm Longitudinal muscular coat 



(somewhat pennate). 



m Mouth. 

 7niv Ventral mesentery. 

 msd Dorsal mesentery. 



np Nephridia. 



718 Nerve-centre. 

 7it Nerve-cords. 



ffi fEsophagus. 

 ov Ova. 



r Rectum. 

 rm Radiate muscles. 

 rh Blood-vessels. 



vc Vascular spaces in region behind 

 tentacles. 



Vt Stomach. 



Fig. 1. Transverse section of tlie anterior region about the level of the anus. The brancliial 

 meshes occur externally, the great vascular spaces, vs, just within these ; while the anus and the 

 uephridial channels have also come in the line of section. The pharyngeal region of the alimentary 

 canal is seen at al. The nerve-tissue is indicated at iv ; and the anterior ends of the posterior 

 body-cavities at 6cl x 40 diam. 



Fig. 2. Transverse section of the posterior region of the body of the Australian Phoronis, showing 

 the reproductive organs — ovr, ovary ; t, testis. Between these organs various blood-vessels are 

 observed — vt, stomach ; mi, intestine. X 40 diam. 



Fig. 3. Transverse section of the tip posteriorly — with the peculiar glandular organ {gls). The 

 muscular layers {ml) of the body-wall have largely mingled, so that they cannot be individually 

 separated. The centre of the glandular organ is filled with glandular tissue, and it has externally 

 basement- and muscular tissue with endothelium, x 80 diam. 



Fig. 4. A further stage in the structure just described — in a section behind the former. The 

 organ has now become connected by its basement-tissue with that in the body-wall, and a lumen 

 appears in the centre. X 80 diam. 



Fig. 5. Transverse section of the tip behind the foregoing, showing the transference of the 

 lumen of the canal of the glandular structure quite outside the basement-tissue, and, indeed, to 

 the thick hypoderm of the region. The muscular coat {ml) consists of intermingled fibres, which 

 thus cross to complete the body-wall posteriorly, x 120 diam. 



Fig. 6. Longitudinal section of the folded hypodermic tissue attached to the left mesentery in 

 the posterior division of the body-cavity. It rests on a considerable layer of basement-tissue. 

 X 350 diam. 



