On the Development of some Japanese 

 Echinoderms. 



Preliminary Notice. 



By 



Dr. Th. Mortensen. 



One of the foremost objects of my recent visit to Japan and 

 other places in the Pacific was to study the development of as many 

 different species of Echinoderms as possible with the view of making 

 a comparative stud)- of the larval forms, in order to see if there is 

 any real interrelation between the shape and structure of the larvae 

 and the natural relationship of the grown-up forms of Echinoderms. 

 Should it prove to be a rule that within an order or family the larvae 

 all possess certain characters in common, one may be justified in 

 drawing conclusions from the characters of the larvae as to the rela- 

 tionship of the mature forms, and thus obtain certainty in cases where 

 doubt reigns as to the natural position of these. 



This is exactly the case with some common Japanese Echini. 



I may recall the fact that I have in my "Ingolf" Echinoidea (I) 

 made a complete rearrangement of several groups ot Echini, both 

 families and genera, e.g. the genera Echinus and Strongylocentrotus, 

 to which were previously referred a great number of species, which, 

 according to my views, ought to be referred not only to different genera 

 but even to different families. I thus maintained that the species 

 Strongylocefitrotus tuberculatus and depressus are no true Strongy- 

 locentrotus, but that the former belongs to the genus Toxocidaris of the 

 family Echinometridce, and the latter to a separate genus, Psendocentrotus, 



