PLATE II. 



Figs. 4-G. Bonellia suhmii, n, sp. 

 Fig. 4. The internal structure of the very imperfect specimen represented in fig. 3; 

 natiu'al size. 



i, i. Intestine. 

 n, n. Nerve-cord. 

 0. Mouth. 



22. The two anal vesicles. 



U. Uterus. 



Y. Tom loop of the intestine. 



Fig, 



The uterus, with low power. 



T. Ciliated funnel. | m. Efferent aperture. 



Fig. 6. The anterior half of an anal vesicle, with medium power. 



Figs. 7-10. Male of Bonellia viridis, Eol., from Trieste. 



Fig. 7. Adult male 1^ mm. long, with high power. The two hooks had fallen off. 

 nervous system could not be demonstrated. 



Eody-cavity. 



The 



h. Anterior blind end of the intestine, attached to 

 the parenchymatous tissue by means of 

 contractile muscle-fibres. 



V. Posterior blind end of the intestine, kept in 

 situ by means of isolated muscular fibres. 



c. Green wandering cells, containing chlorophyll. 



d. Connective substance. 



e. Ciliated epithelium. 

 /. Vesicular cells. 



rj. Generative opening, and near it some expelled 



spermatozoa. 

 i. Intestine. 



Musculature. 



Contractile fibres. 



Nuclei of the peritoneal epithelium. 



Spermatozoa. 

 s. The right anal vesicle (Analkieme) — seg- 

 mental organ. 

 s'. The left anal vesicle ( Analkieme) — segmental 



organ. 

 vcl. Vas deferens. 



y, y. External apertures of the segmental organs. 

 z. Contents of the intestine. 



Fig. 8. Cross section in the region A of fig. 7, drawn with the aid of the camera lucida 



from a chrom-osmic acid preparation. 



n. The inferior swelling of the oesophageal ring (the first pair of ventral ganglia). 

 The other letters are as in fig. 7. 



Fig. 9. Cross section in the region B of fig. 7. Letters as above. 



Fig. 10. One of the so-called anal vesicles (segmental organs), with very low power. The 

 right is always somewhat smaller, and lies somewhat further back than the 

 left. Each of these segmental organs opens separately to the exterior, 

 ventrally and laterally. By the contractions of the body- wall the blood 

 of the body-cavity and with it the free funnels of the segmental organs 

 are driven backwards and forwards. The rim of the funnel is formed of 

 from five to seven ciliated cells. The lumen of the segmental duct is 

 ciliated, but only interruptedly, not continuously. 



V. Wall. 



u. Lumen with lash-like cilia. 



X. Funnel opening. 

 z. Exterior opening. 



