338 



MESSES. C. SHEARER, W. DE MORGAN, AND H. M. FUCHS 



origin. This pigment persists to a much later stage than shown by these figures, and 

 is not, perhaps, sufficiently brought out in fig. 103. 



On the whole, therefore, we may conclude that this cross resembles the maternal 

 parent more than the paternal, and this is clearly shown by the primary spine of the 

 ambulacral plates, the colour of the test and spines, and the plates on the buccal 



Text-fig. 19. 



Text-fig. 20. 



Text-fig. 1 9. — Pedicellari* of E. miUavis. A, lateral view ; B, full view, x 1 70. 

 Text-fig. 20.- Pedicellarise of the cross E. milaris ? x ^. acutus^ . A, lateral view ; B, full view, x 170. 



membrane. On the other hand the pedicellarije are partly paternal, which is shown 

 by the tridentate and the triphyllous, which are of the pure E. acutiisiy^e, while the 

 globiferous are intermediate between both parent species. The size again approaches 

 more that of E. miliaris than that of E. acutits. None of the hybrids of this cross 

 have shown any tendency to grow rapidly or seem likely to surpass in size the 

 maternal parent. 



16. General Discussion. 



In this paper we have given a full account of an investigation into the inheritance of 

 parental characters in hybrids between three species of Echinus, the experiments 

 extending over a period of four years. What evidence could be obtained as to the 

 inheritance of the somewhat indefinite and variable characters of the young larvfe has 

 been detailed, but the major portion of the work is concerned with the transmission of 

 definite and fixed characters of the late larvte, and with the characteristics of the 

 hybrid urchins after metamorphosis. The accomplishment of the investigation has 

 been due to the elaboration of methods of rearing the larvee and young urchins in 

 the laboratory imder conditions as nearly approaching those of nature as possible. 



