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



Fig. 96. — E. acutus % X E. miliaris $ immediately after metamorphosis. Note 

 the single primary tube-foot in each radius, as in the maternal parent. 

 This individual had unusually long spines. 



Fig. 97. — E. miliaris % X E. acutus $ immediately after metamorphosis. There 

 was a single primary tube-foot in each radius, as in the paternal parent. 



Plate 24. 

 Figs. 98-107. — Older Echini raised in the laboratory. 



Fig. 98. — Aboral view of E. miliaris raised in the laboratory from the egg. The 

 drawing represents the animal, natural size, when it was about eight 

 months old. Its spines remained the same length as the test grew larger, 

 and when the animal had attained full size, at about the twelfth month, 

 they looked relatively much shorter in proportion to the size of the test 

 than shown in this figure. The animal is the long-spined variety although 

 both its parents were of the short-spined type from Cawsand Bay. This 

 animal discharged ripe eggs under laboratory conditions, in the latter part 

 of May, 1913, thus breeding within the first year of its existence. 



Fig. 99. — Aboral view of an urchin of ^. csculent,us raised in the laboratory from the 

 egg. The figure represents the animal at the age of four months. X 3. 

 The markings on the spines are very prominent at this age. 



Fig. 100. — Aboral view of urchin of the cross E. esculerdus % X E. acutus $ , five 

 months old. X 3. These hybrids grew very much faster than any 

 of the others and seemed very hardy. This individual shed its primary 

 spines through ill-health at the sixth month, but grew new ones, 

 and at the end of the first year measured some 8 or 9 cm. in diameter. 

 At this stage the pigmentation of the test and spines is very different 

 from that shown at the end of the first year, which is shown in fig. 104. 



Fig. 101. — Aboral view of young urchin of the cross E. acutus % X E. miliaris $ . 



This cross grew very slowly after metamorphosis. The figure represents 



their appearance at the age of four months. X 10. 

 Fig. 102.- — Aboral view of a young urchin of the cross E. miliaris ^ X E. esculentus $ . 



Five months old. This urchin was derived from one of the cultures of 



1912 in which the inheritance of the ciliated epaulettes was in some larvaj 



maternal, in others paternal. X 15. 

 Fig. 103. — Aboral view of urchin of the cross E. miliaris $ X E. acutus $ , one year 



old. This urchin is shown at the age of four months in fig. 105. X 5. 



Another variety of the same cross is shown of the same age in fig. 107. 



In figs. 105 and 107 the green pigment of E. miliaris does not show as it 



does in the older hybrid shown in fig. 103. Fig. 103 is represented twice 



natural size. 



