Notes on the Larval Skeleton of Spatangus 
purpureus. 
By 
Hiroshi Ohshima, 
Assistant Professor in the Department of Agriculture, Kyushiu 
Imperial University, Fukuoka, Japan. 
With Plate 21. 
AuruougcH ‘one of the very first Echinoderms of which 
artificial fertilization and rearing of the larvae were under- 
taken’ (Mortensen, 6, p. 14), the development and 
especially the structure of the larval skeleton of Spatangus 
purpureus have been rather imperfectly known. Krohn’s 
descriptions and figures (2, 8) are not quite satisfactory with 
regard to the skeletal structure, and, moreover, the larvae 
described in his second paper are doubtful as to their specific 
identification (Mortensen, 6, p. 15). Through Mor- 
tensen’s renewed observations on the artificially-reared 
larvae of this species (6, pp. 14-17) the external features of 
the larval development are now made clearer. As to the 
larval skeleton, however, he was only able to give some brief 
information owing to the unfortunately bad state of preserva- 
tion of his specimens. Among other Spatangoids, E¢hino- 
cardium cordatum and Brissopsis lyrifera were 
carefully studied by Macbride (4) and Mortensen 
(7, pp. 144-8), and the larvae of these three species have been 
shown to have such a striking resemblance to each other in 
early stages that it is desirable to ascertain some more minute 
diagnostic characters for each species. In such circumstances 
