472 
E. W. 3EA0BRIDE. 
meet by means of sections, but tlie necessary leisure for this 
seems still to be a long way off, and it seems worth while in 
the meantime to place on record the external features of the 
development of a Spatang'oid. 
Our knowledge of the complete life-history of echinoid 
larvas is still extremely scanty ; indeed, the only species in 
which the external features of the development have been 
completely described are the Clypeastroid, Echinocyamus 
pusillus, described by Theel (1892), the endocyclic urchins 
Echinus esculent us and E. miliaris described by myself 
(1903), and quite recently Strongylocentrotus lividus 
described by von Ubich (1913). 
The larva of Echinocardium cor datum was first seen 
by Johannes Muller (1846). He described the later phases of 
larval life immediately preceding metamorphosis : he was able 
to identify the larva as the larva of some echinoid but which 
echinoid he was quite unable to say. His figures, howevei*, 
leave no doubt in my mind that he was dealing with the larva 
of Echinocardium cor datum. Tlie early larva of Spa- 
tan gus purpureus was described by Krohn (1853), who 
reared it from artificially fertilised eggs, and his work has 
been repeated and confirmed by Mortensen (1913), who kept 
the larvae alive for three weeks. 
The younger stages in the larval development of Echino- 
cardium cordatum were described by Vernon (1898) and 
more recently by myself (1912). The fully developed larva 
was described and figured by Mortensen (1901) but the 
identification of his specimens as the larvae of Echino- 
cardium cordatum rests on a mere guess because the 
ground of the identification was the occurrence of the larva 
in question in the waters of the Lymfiord in Denmark on the 
sandy bottom of which E c h i n o c a r d i u m c o r d a t u m was the 
only Spataugoid which was found. 
I have to express my thanks to the Director of the Millport 
Station, Mr. Kichard Elmhirst, for his kindness to me during 
my stay in Millport and for the assistance which he rendered 
me in carrying out my experiments. 
