NOTES ON THE STRUCTUEE OF OIKOPLEURA. 47 



Section 254, nervous system, sense organs, &c. 

 Section 257, part of the centre, showing nervous 



system, &c., highly magnified (X 600). 

 Section 266, showing anterior end of nervous 



system, oral glands, &c. 

 Dorsal part of last section more highly magnified 



(X 600). 

 Diagrammatic reconstruction of the animal from 

 the sections, seen from the right hand side, 

 showing the extent of the thickened ectoderm 

 and test dorsally and ventrally, the course of 

 the nerve cord, and the shapes, sizes and 

 relative positions of the other organs, about 60 

 times natural size. 

 PosT-scEiPT. — March 1 ;— Mr. W. Garstang, who was 

 present when this paper was read, has kindly 

 written to me since stating that in some sections 

 of Oikopleura (? dioica) which he has made the 

 endostyle is an open canal in the greater part of 

 its extent. On the other hand Dr. Bousfield has 

 very kindly sent me three additional series of 

 sections of the same species of Oikopleura as 

 before {? flabellum), and in these I find as in the 

 one described above that the cavity of the endo- 

 style is shut off from the pharynx above for 

 rnore than half of its length. The actual numbers 

 of sections involved in these new series are : — 

 I. closed posterior 7 sects., open 14, closed anterior 12. 



n. „ 6 „ 14, „ 11. 



III. „ 10 „ 18, „ 19, 



