2&6 MESSRS. C. SHEARER, W. DE MORGAN, AND H. M. FUCHS 



(9) E. miliaris ^ X E. acutus $ . {Cf. Plate 21, figs. 67-72.) 



45 hours. Gastrulse. 

 90 ,, Early plutei. 



7 days. Plutei wliich were remarkable for their long antero-lateral arms. The 



pigment was very variable. In some it was close, covering nearly the 



whole pluteus with a network of small dots and lines ; in others it was 



scanty and arranged along the ciliated margins. 

 11 ,, Appearance of postero-dorsal arms and skeleton of preoral arms. The 



plutei were variable in form. Most had the wide and stumpy arms and 



sparse pigmentation of E. miliarU, and a few the long arms and 



stippled pigmentation of E. acutus. 

 27 „ ^c/tm«s-rudiment present. Anterior epaulettes with the green pigment 



masses. 

 58 ,, Two were on the point of metamorphosing. Others had well-advanced 



-£'c/iTOWs-rudiments and two lateral pedicellarise. No posterior ciliated 



epaulettes were developed. 



It remains to draw attention to one general feature that is shown by all the 

 characters in the hybrids : that is, that their rate of development is usually much 

 slower than in the pure forms. Thus the posterior ciliated epaulettes in the cross 

 E. esculentus ? X E. miliaris $ appear usually later, and their growth is much 

 slower than in the pure E. esculentus. Moreover, as we have mentioned, their 

 connection with the ciliated band from which they are formed is usually retained, 

 while in the pure-bred larva of E. esculentus this connection is completely severed. 

 In short, in the hybrid the presence of a posterior epaulette never reaches the same 

 degree of development as in the pure form. In a like degree this applies to the 

 skeleton, pigment, and pedicellaria Thus the presence of the posterior ciliated 

 epaulette, posterior pedicellaria, green pigment, when inherited through the egg or 

 sperm in hybrids, is never accompanied by the rate of growth, or marked by the 

 attainment of the same size, as that characteristic of their condition in the 

 pure forms. 



8. The Inheritance of the Larval Skeleton. 



In the large number of papers that have appeared on the subject of Echinoderm 

 hybridization the skeleton has been selected as the principal structure that has been 

 used ill elucidating parental influence. This has been in great part due to the fact 

 that in the early pluteus, from four to seven days old, the skeleton is one of the most 

 obvious features. In many of the forms investigated, this structure has quite a 

 different arrangement ; in some, the postoral arm skeleton being arranged in the form 

 of smooth calcareous rods ; in others, the skeleton throughout is highly toothed or 

 covered with spinous processes ; while again in others, the postoral rods are multiple 



