ON PHYMOSOMA VARIANS. 97 



DESCRIPTION OF PLATES VII, VIII, IX, and X,» 



Illustrating Mr Ai-thur E. Shipley's paper 

 "On Phymosoina varians." 



PLATE VII. 



Fig. 1. — A semi-diagrammatic view of the anterior end of Phy mosoma 

 varians. The introvert is everted and the tentacular crown e.xpauded. 

 The collar is not extended and lies at the base of the head. Only two rows 

 of hooks are shown. 



Fig. 2. — A semi-diagrammatic view of the closed vascular system and 

 nervous system, showing their relation to the alimentary canal. The 

 vascular system shows the three parts, the lophophoral, the lower lip, and 

 the dorsal blood-vessel. The latter communicates with the lophophoral in 

 the middle line, and just at this point the sinus round the brain is given 

 off. The brain is relatively too small. The three main nerves are shown, 

 and the circular nerves which run in the skin. The oesophagus is cut oft' 

 abruptly in front in order to display the vascular ring. 



Fig. 3. — View of a Ph. varians which has been opened along the 

 median dorsal line. The introvert is retracted, the true anterior end of 

 the body being where the eye-spots lie. Here and there patches of skin 

 are seen which bear papillae. 



PLATE VIIL 



Fig. 4. — A median longitudinal section through the head. The intro- 

 vert is retracted, and the collar expanded until it encloses the whole head. 

 The section is not quite in the middle line, or the lip on the dorsal surface 

 would not be shown, cf. Fig. 6. The brain is cut through that part which 

 is continuous with the ectoderm. 



Fig. 5. — A trans\erse section through the tentacles : the introvert is 

 retracted. The tentacles show the ciliated groove on the outer surface, 

 the pigmented epithelium in the inner, and the vascular spaces and 

 tentacular nerves. 



Fig. 6. — A transverse section through the base of the lophophor and 

 lower lip, just where the two fuse dorsally : the introvert is retracted. The 

 skeletal tissue is shown in the lip, which is ciliated all round. 



Fig. 7. — An oblique transverse section through the base of the lopho- 

 phor, showing the blood-space ; and in the centre some of the wrinkled 

 pigmented tissue of the prseoral lobe. The introvert is everted. 



1 I am indebted to Mr Weldon for the following tigures :— Nos. 1, 7, 10, 12, 

 14, 15, If;, 20, 21, 2.S. and 27. 



