EXPLANATION OF THE PLATES 



Sonic of till' lii;ui(.'s ol ( )|)liiuri<l-laivii' wtTc drawn \>\ .Mr. 1. Litliu rk i n<l , who lias also 

 drawn sonic of the skeletal lif>urcs of Hicsc larva' given in llie text. I l)cg lo ex|)ress here 

 my indehledness to .Mr. Lieberkind for his valuable assistance. 



Plate I. 



i'ig. 1. l.arva of Evhiiwmclru lucunler (Linn.), two weeks old, fully fornieil: 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 |)ostoral 

 arm is seen the beginning amniotic invagination. Drawn from life, '""/i- 



Plate II. 



Fig. 1. Larva of 't'rii>iuiisl(s csiiiltntiis (Leskc), 17 days old; from llic ventral side. Drawn 

 from life. '-^"/i. , 

 2. Larva of same species, 22 days old; from the dorsal side. ,\t I he 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. I.) is due lo pressure of llic larva under the cover. Drawn from life. '*°/j. 



Plate III. 



I'ig. I. Larva of Lijlirliiitiin rarifyalus (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. '^°/,. 

 2. Larva of same si)ecies, 1.") days old. seen from the ventral side. Drawn of life, '^"/i- 



Plate IV. 



l'"ig. 1. Larva of AslriclinH'iis Maniii Verrill. ti days okl; seen from the ilorsal side. am. 



amnion. Drawn from life. '^" ,. 



2. Larva of Mcllila si'.ri(:iper/i}r(ilu (Lcske). 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 mil be discerned. 



200/ 



Plate V. 

 Fig. 1. l^mbryo of ICticidaris Tlwuarsi (Val.), :i days old. '^'^'i- 



2. Young larva of same s|)ecies. (i days old, slightly restored. I'lie skeleton dissolved. 

 The small bo<l\ to Ihc left of (he mouth probably represents part of the enterocoel. 



;{. Section of voung embryo of I'hijllacanlhus parvispinus Woods, in the blastula stage. 



■•»/,. 

 I. Section of embryo in the gastrula stage of same species, ""/i. 

 5. Larva of Diadema antillarum Phil., ."> days old: from the ventral side. Drawn from 



