358 MESSRS. C. SHEARER, W. DE MORGAN, AND H. M. FUCHS 



Fig. 69. — Four-armed pluteus. 9 days. X 100. From the dorsal aspect. Com- 

 mencement of jDreoral and postero- dorsal arms. 



Fig. 70, — Six-armed pluteus. 17 days. X 55. From the dorsal aspect. Arms 

 unusually long. Development of the anterior ciliated epaulettes. 



Fig. 71. — Eight-armed pluteus. 20 days. From the ventral aspect. Development 

 of the green pigment patches characteristic of E. miliaris. Appearance 

 of the -E'c/mms-rudiment. 



Fig. 72.— Pluteus. 58 days. X 55. From the dorsal aspect. Note the absence of 

 posterior ciliated epaulettes. 



Plate 22. 



Figs. 73-79. — Fully-formed hybrid plutei from the experiments of 1912. 

 Fig. 73. — E. esculentus ^ X E. milimis $ . Dorsal view of larva vs^ith maternal 



characters, presence of posterior ciliated epaulettes, and absence of green 



pigment masses. 

 Figs. 74-76. — -Plutei from a culture of the cross E. esculentus % X E. miliaris $ in 



which the inheritance of the posterior ciliated epaulettes was of an 



exceptional nature (see p. 305). All the plutei had the maternal 



absence of green pigment. 

 Fig. 74. — Larva with both posterior epaulettes. 



Fig. 75. — Larva with a posterior epaulette on one side of the body only. 

 Fig. 76. — Larva with neither posterior epaulette. 

 Fig. 77. — E. miliaris ^ X E. esculentus $ (the reciprocal of fig. 73). Dorsal view 



of larva with pa^ernaZ characters, presence of posterior ciliated epaulettes 



and absence of green pigment. 

 Fig. 78. — E. aculus % X E. miliaris $ . Dorsal view of larva with maternal 



characters — presence of posterior epaulettes and absence of green 



pigment. 

 Fig. 79. — E. miliaris % X E. acutus $ (the reciprocal of fig. 78). Ventral view of 



larva with paternal characters — presence of posterior epaulettes and 



absence of green pigment. 



Figs. 80-83. — Fully-formed plutei of crosses between E. acutus and E. miliaris 

 reared from eggs which had been fertilized in waters of changed OH-ion concentra- 

 tion. Experiments of 1 9 1 1 . 



Fig. 80.—^. acutus % X E. miliaris $. 27 days. 0-5 c.c. N/10 NaOH per 

 200 c.c. sea-water. Note the maternal characters — presence of posterior 

 epaulettes and absence of green pigment. 



Fig. 81. — The same cross. 34 days. 0'5 c.c. N/10 acetic acid per 200 c.c. sea- 

 water, Maternal characters. 



