ON THE EXPERIMENTAL HYBRIDIZATION OF ECHINOIDS. _ 285 



(6) E. esculentus % X E. miliaris $ . {Cf. Plate 20, figs. 44-52.) 



65 hours. Gastrulse. 

 4 days. Prism larvse with scattered pigment spots. 



8 ,, Apex of larvae dome-shaped. Apical rods spinous. Commencement of 



skeleton of postero-dorsal and preoral arms. 



11 ,, Anterior ciliated epaulettes appeared. 



14 ,, Appearance of ^c/jm«.s-rudiment. 



27 ,, Posterior ciliated epaulettes apjjeared. 



36 ,, Anterior ciliated epaulettes completed. ^c/w'y/M.s-rudiment with tube-feet. 



Posterior and lateral pedicellarise. 



(7)]^. miliaris % X E. esculentus $ . {Cf. Plate 21, figs. 53-59.) 

 Few larvse resulted from this experiment, but they developed very quickly. 



65 hours. Transparent prism larvse, with slight pigmentation resembling E. milim-is. 

 7 days. Postero-dorsal arms growing out. Skeleton of preoral arms appearing. 

 Slight pigmentation. 



12 „ ii'c/!Mm.s--rudiment present and anterior ciliated epaulettes with green 



pigment masses. Later green pigment appeared also at the exti'emities 

 of the arms and in the oral lobe. 



Neither the posterior ciliated epaulettes nor the posterior pedi- 

 cellariae appeared. 

 40 ,, Some had metamorphosed and others metamorphosed later. 



(8) E. acutus % X E. miliaris $ . {Cf. Plate 21, figs. 60-66.) 



45 hours. The larvse were rather backward, the majority being only in the blastula 

 stage. 

 3 days. Prism larvse with the antero-lateral and postoral arms commencing. 

 6 ,, Plutei, which were but slightly pigmented. Long oral lobes. Apical 



rods spinous. 

 10 ,, Neither the postero-dorsal nor the preoral arms had yet appeared. The 



shape, length of arms, and pigmentation resembled E. acutus. 



15 ,, Anterior ciliated^ epaulettes, preoral and postero-dorsal arms appeared. 



27 „ Echinus-rudiment present. Anterior ciliated epaulettes complete. Three 



pedicellarise, one posterior and two lateral. 

 40 ,, Posterior ciliated epaulettes present. 



80 ,, All but a dozen had died ofiF. These had the three pedicellarise and were 



on the bottom of the jar, about to metamorphose. 



