EXPLANATION OF THE PLATES 



Some of the figures of Ophiurid-larvee were drawn by Mr. I. Lieberkind, who has also 

 drawn some of the skeletal figures of these larvae given in the text. I beg to express here 

 my indebtedness to Mr. Lieberkind for his valuable assistance. 



Plate I. 



Fig. 1. Larva of Echinometra lucunter (Linn.), two weeks old, fully formed; seen from the 

 ventral side. Drawn from life. ^'"/i. 

 2. Larva of same species, same age; from the dorsal side. At the base of the left postoral 

 arm is seen the beginning amniotic invagination. Drawn from life. ^^Vi- 



Plate II. 



Fig. 1. Larva of Tripneustes esculentus (Leske), 17 days old; from the ventral side. Drawn 

 from life. '^o/^. 

 2. Larva of same species, 22 days old; from the dorsal side. At the base of the left 

 postoral arm is seen a small invagination, the amnion. A pedicellaria has begun 

 to form in a groove in the posterior end. The forward direction of the ventral ciliated 

 lobes (v. 1.) is due to pressure of the larva under the cover. Drawn from life. ^^"/j. 



Plate III. 



Fig. 1. Larva of Lytechinus variegatus (Lamk.), 13 days old, seen from the dorsal side. 

 Drawn from life. The amnion has been formed and in the posterior end a pedicel- 

 laria (p) is beginning to develop, ^^"/i- 

 2. Larva of same species, 15 days old, seen from the ventral side. Drawn of life. i*»/i- 



Plate IV. 



Fig. 1. Larva of Astriclypeus Manni Verrill, 6 days old; seen from the dorsal side. am. 



amnion. Drawn from life. ^*7i- 



2. Larva of Mellita sexiesperforata (Leske), 7 days old; seen from the dorsal side, turned 



slightly upwards; in beginning metamorphosis. Drawn from life. On account of 



the opacity of the larva the details of the body skeleton could not be discerned. 



200/ 



Plate V. 



Fig. 1. Embryo of Eucidaris Thouarsi (Val.), 3 days old. ^^Vi- 



2. Young larva of same species, 6 days old> slightly restored. The skeleton dissolved. 

 The small body to the left of the mouth probably represents part of the enterocoel. 



3. Section of young embryo of Phyllacanthus parvispinus Woods, in the blastula stage. 



4. Section of embryo in the gastrula stage of same species, ^^/j. 



5. Larva of Diadema antillarum Phil., 5 days old; from the ventral side. Drawn from 



