ON THE EXPERIMENTAL HYBRIDIZATION OF ECHINOIDS. 357 



Fig. 54. — Pluteus. 7 clays. X 100. From the dorsal aspect. Commencement of 



the postero- dorsal arms. 

 Fig. 55. — Pluteus. 9 days. X 100. From the ventral aspect. Commencement of 



the preoral arms. 

 Fig. 56. — Pluteus. IG days. X 100. From the dorsal aspect. Commencement of 



the anterior ciliated epaulettes. 

 Fig. 57. — Pluteus. 33 days. X 55. From the dorsal aspect. Appearance of the 



^cAmMS-rudiment, and of the green pigment masses typical of 



E. miliaris. 

 Fig. 58. — -Pluteus. 40 days. X 55. From the dorsal aspect. Note the absence of 



posterior ciliated epaulettes. 

 Fig. 59. — Pluteus. 30 days. X 55. From the ventral aspect. This larva has 



developed more rapidly than those shown in figs. 57 and 58. The Echinus- 



rudiment is seen with tube-feet projecting. The arms are being retracted, 



preparatory to metamorphosis. 



Figs. 60-66. — E. acutus % X E. miliaris $ , 1909-11. 



Showing, in the fully-formed plutei, the maternal inheritance of the posterior 

 ciliated epaulettes and absence of green pigment masses. 



Fig. 60. — Prism larva. 3 days. X 110. From the dorsal aspect. 



Fig. 61. — Pluteus. 5 days. X 100. From the dorsal aspect. Antero-lateral and 



postoral arms present. 

 Fig. 62. — Pluteus. 8 days. X 100. From the dorsal aspect. 

 Fig. 63. — Pluteus. 15 days. X 55. From the dorsal aspect. Commencement of 



preoral and postero-dorsal arms and of anterior ciliated epaulettes. 

 Fig. 64. — Pluteus. 22 days. X 55. From the dorsal aspect. 

 Fig. 65. — Pluteus. 27 days. X 55. From the dorsal aspect, ^c^mws-rudiment 



present. Anterior ciliated epaulettes complete, but posterior epaulettes 



not yet formed. Posterior pedicellaria present. 

 Fig. 66. — -Fully-formed pluteus. 40 days. X 55. From the dorsal aspect. 



Posterior ciliated epaulettes developed. 



Figs. 67-72. — E. miliaris ^ X E. acutus $ , 1909-11. 



Showing, in the fully-formed plutei, the maternal inheritance of the green pigment 

 masses and absence of posterior ciliated epaulettes. 



Fig. 67. — Prism larva. 65 hours. X 180. From the ventral aspect. 

 Fig. 68. — Early pluteus. 4 days. X 180. From the ventral aspect. Commence- 

 ment of antero-lateral and postoral arms. 



