14 HJALMAR THÉEL, XOTES ON THE DEVELOPMENT OF ECHINOCARDIUM AND PARECH1NUS. 



Explanation of the plate. 



Pluteus of Echinocardium cordatum (Penn.) scen from the dorsal surface: eleven days old; raised 

 in tlic aquarium from artificially fcrtilizcd eggs. Length of the larva 0,: mm. 



Side view of a young sea-urchin of Echinocardium cordatum (Penn.), hatched in the aquarium from 

 more advanced plutous-larva- caught from the surface of the sea. Highly magnified. 



The same as hefore, scen from the under surface. 



Upper \iiw of a ymnig sea-urchin of Parechmus miliaris (L.), raised in the aquariam from artificially 

 fertilized eggs. Ilighly magnified. 



Fig. 5. — Under view of the same. 



Fig. 



i. 



Fig. 







Fig. 



3. 



Fig. 



4. 



1 1 .Ki den 2 augusti 1912. 



Umqvlat I rl«A B. 



