It is a great pleasure to me to dedicate this small paper to my old friend Professor 

 Gustaf Retzius, as a humble tribute to the celebration of his 70 th birthday. On 

 such a solemn occasion I should liave desired to make a contribution of greater 

 value, but urgent duties have not permitted me to do so. The present »Notes» may 

 properly be looked upon as a completion of our knowledge of the earlier stages of 

 the development of the Echinids. 



I must admit, however, that it is with a certain delight that I dedicate these 

 notes to Gustaf Retzius, for my investigations, which were commenced many years 

 ago (1892 — 1894) will, no doubt, evoke in him the memory of the many happy 

 days \ve spent together at our beloved marine station, Kristineberg. For more than 

 30 years we met almost yearly at Kristineberg and we spent our summer-seasons there 

 in working at the solution of various scientific questions. He, especially, worked 

 with an interest and energy quite unparalleled and unprecedented. For this work 

 Swedish biological Science is decply indepted to him. 



But Science is cosmopolitan, and I am convinced that scientists of all nations 

 concur with me in the opinion that the works of Gustaf Retzius are highly appre- 

 ciated all över the world. 



In 1892 and the following years, when I was working at the development of 

 Echinocyamus pusillus (O. F. Muller) and Parechinus miliaris (L.), I also devoted 

 my attention to the development of Echinocardium cordatum (Penn.). With regard 

 to the two former species my experiments were successful. I was able to follöw their 

 development step by step, from the artificially fertilized egg to the stage when the 

 young sea-urchin has sunk and settled on the bottom of the aquarium, the larva 

 having passed through all the metamorphoses in captivity. 



With regard to Echinocardium cordatum (Penn.), on the other hand, there was, 

 of course, no difficulty in impregnating the eggs in an artificial manner and bringing 

 about a development in the aquaria, but after about a week or slightly more the 



