ON THE EXPERIMENTAL HYBRIDIZATION OE EGHINOIDS. 



307 



As mentioned above, the percentage of eggs which fertihzed in this cross was low. 

 In one case only did a large number of the eggs develop, and the larvae produced 

 were of two types. 10 were of purely paternal form, having posterior epaulettes 

 and no green pigment, while 25 were of the purely maternal type in general form 

 and in having no posterior ciliated epaulettes and developing the green pigment 

 masses. 



Crosses hetween E. acutus and E. niillaris. 



1. E. aciitus '^ X E. miliaris $ — 



With one exception., all the fertilizations of this cross gave larva) with maternal 

 characters, as in previous years. The posterior ciliated epaulettes were developed 

 and the green pigment was absent (Plate 22, fig. 78). 



In the exceptional case all the larvae had the maternal absence of green pigment, 

 but some had both posterior epaulettes, some had an epaulette on one side of tlie 

 body only, and others neither posterior epaulette. 



2. E. miliaris'^ x E. acntns^ — 



Without excejition, all the cultures of this cross gave purely paternal plutei, ivhicit 

 ivas the reverse of the inheritance in previous years. The larvse developed both 

 posterior ciliated epaulettes and had no green pigment (I'late 22, fig. 79). 



Excluding for the present the exceptional cases, it will be seen from the foregoing 

 that the crosses E. cscvlentus% X E. miliaris^ and E. acuttis % X E. miliaris (S 

 showed a maternal inheritance in 1912 as in 1909-11, while the crosses E. nnliaris ? X 

 E. esculentus $ and E. miliaris % X E. acutus $ changed from a maternal to a 

 paternal inheritance. Compare text-fig. 12 with text-fig. 10. 



Text-FIG. 12. — Diagram to show the inheritance of the late larval characters in hybrids between 

 E. miliaris and E. acutus during 1912 ((/. text-fig. 10). p.nl.ep., posterior ciliated epaulette. 



2 R 2 



