THE EXPERIMENTAL HYBRIDIZATION OF ECHINOIDS. 133 



There is only one set of epaulettes, the anterior, and they gradually 

 close together and encircle the anterior pole of the body. They are 

 dotted with yellowish brown pigment, generally of a lighter shade 

 tlian in E. escuJaitm^, and carry strong cilia. 



There are two pedicellariae on the right side, one dorsal and one 

 ventral ; the latter not being shown in the figure. On the left of the 

 stomach is the Echinus rudiment. Between this stage and meta- 

 morphosis there is not much change except in the size of the Echinus 

 rudiment, and the amount of green pigment. 



The chief external features are : — 



Anterior epaulettes only. 

 Two pedicellariae. 



One right side dorsal. 



One right side ventral. 

 Masses of bright green pigment. 



E. ESCULENTUS S 

 (d) EARLY DEVELOPMENT OF ^. miliaR1S9 



The four-armed plutei differ but little from the pure K miliaris 

 larvse of the same stage, excepting that they carry rather more 

 pigment. A preoral lobe is present, but is not marked as in pure 

 £. miliaris. The typical elongated B. miliaris shape is retained until 

 about the time when the epaulettes make their appearance, when 

 the posterior pole gradually assumes a flatter curve as in the figure. 



EXTERNAL CHARACTER OF LATE LARVA (FIG. 4). 



The body is not so deep, and the arms are longer than those of the 

 pure B. miliaris, but the general appearance is very similar. The 

 whole body, and the ciliated bands, are spotted with pigment of various 

 shades of reddish brown. 



There is besides a large mass of green pigment at the bases of the 

 epaulettes, and another mass of the same has appeared between their 

 ends, and later on more will probably appear. 



There is only one set of epaulettes, which ultimately encircle the 

 anterior margin of the body. They are spotted with brown pigment 

 and carry strong cilia. 



There are two pedicellariae, one dorsal and one ventral, on the 

 right side (the latter not shown in Fig. 4). 



