A STUDY OP METAMERISM. 473 



38. Wilson, E. B. — " Embryology of the Earthworm," 'Journ, Morph.,' 



iii, 1889. 



39. WiLLEY, A. — " Studies on the Protochordata :" I, ' Quart. Journ. Micr. 



Sci.,' xxxiv, 1893. 



40. WooDWAKD, M. F. — " Description of an Abnormal Earthworm possess- 



ing Seven Pairs of Ovaries," ' Proceed, Zooi. Soc.,' 1892. 



DESCRIPTION OF PLATES 40—43, 



Illustrating Mr. T, H. Morgan's paper, '' A Study of 

 Metamerism." 



PLATE 40. 

 Type forms of modification of metameres of Annelids. See pages 395 to 4U3. 



Fig. I, A, B, c, — Compound metamere (split metamere), as seen from dorsal 

 (a), ventral (b) side, and reconstructed in c, as seen from above, 



EiG. II, A B c— Modification of last. 



Fig. Ill, A B c. — Inserted half-metamere. 



Fig. IV, A B c. — Double compound metamere. 



Fig. V, a b c. — Failure of lines to meet dorsally. 



Fig. VI, A, B, c. — Spiral of two metameres. 



Fig, VII, A, B, c. — Spiral, with one more half-metamere on one side than on 

 other. In all five half-metameres. 



Fig. VIII, A, B, c. — Spiral, with same number of half-metameres on each 

 side. In all six half-metameres. 



Fig, IX, A, B, c, — Spiral of type VII, but longer. 



Fig. X, A, B, c, — Spiral of type VIII, but longer. 



Fig. XI, A, B, — Spiral of type VIII, but still longer. 



Fig. XII, A, B, c. — Spiral formed by combination of half-compound meta- 

 meres. 



Fig. XIII. — Spiral, in part a double-spiral, formed by introduction of 

 half-compound metameres. 



Fig. XIV. — Spiral, in part a double-spiral, formed by the introduction of 

 a half-double-compouud metamere. 



