130 CKESSWELL SHEARER, WALTER DE MORGAN, H. M. FUCHS. 



in wandering amoebocytes and is an excretory product in process of 

 removal. 



There are four pairs of long, slender arms, and along their edges run 

 the ciliated bands. Around the anterior margin of the body are the 

 " anterior ciliated epaulettes." These arise as four horizontally placed 

 crescentic bands of cilia, constricted off from the main ciliated band, at 

 the base of the post-oral and postero-dorsal arms. They gradually 

 grow together, and before metamorphosis form a complete ring round 

 the anterior pole of the body. In the figure they have not yet united 

 dorsally. They are spotted with brown pigment, and carry powerful 

 cilia, which in these late stages are the principal means of locomotion. 

 At the posterior end are the " posterior ciliated epaulettes." These 

 are pigmented and ciliated like the anterior epaulettes, and eventually 

 will extend round the posterior pole of the larva. 



There are three pedicellariae : one at the posterior pole, and two on 

 the right side, one dorsal, and one ventral, the latter of which is not 

 seen in the figure. 



On the left hand, lying against the stomach, is the Echinus rudiment. 



Between this stage and metamorphosis there will not be much change 



in the appearance of the larva, except in the increased size of the 



Echinus rudiment and the union of the posterior epaulettes. 



„, , , . , „ ^ T 1 T ^ ^- csculentus ^ 



Thus the salient external features of the late larva of-.z; — ; — 



ii. csadentus 2 

 are : — 



The anterior epaulettes. 



The posterior epaulettes. 



Three pedicellariae. 



One right side dorsal. 



One right side ventral. 



One at the posterior pole. 



E. MILIARIS a: 

 (h) EARLY DEVEL0P:\IENT OF 



E. ESCULENTUS 9 



There was a good deal of variation among the four-armed plutei of 

 this hybrid. The majority inclined to the pointed, clear, lightly 

 pigmented miliaris type, but did not develop a preoral lobe. On the 

 other hand, there were some that showed distinctly csculentus char- 

 acters. In the course of development the posterior pole becomes more 

 rounded, and, when the anterior epaulettes were formed, either the 

 larvffi were distinctly esculent ns in shape, or intermediate between 

 eseulentus and miliaris. The posterior epaulettes did not show much 

 advance until the end of the fourth week, by which time the right dorsal 

 pedicellaria was well established. 



