145 
memoir on the Echinoderm larvæ (p. 23. PI. IX. Figs. 61—64) 
mentions a Spatangoid larva, found off Port Erin in February— 
April, which, he thinks, must be referred to Echinocardium flaues¬ 
cens. Unfortunately he does not point out which are its charact- 
eristic features; judging from the figures it has unfenestrated post¬ 
oral rods, in marked difference from the other Spatangoid-larvæ 
known from North-European seas. Only younger stages are figured 
by Chadwick, with the postero-dorsal arms not yet developed; 
with a curious selfcontradiction he States not having seen a later 
stage, although a few lines above he says that in 1914 „numbers 
of fully developed specimens occurred in the plankton about the 
middle of April“. The reference of this larva to Echinocardium 
flauescens in any case is uncertain ; it should also be pointed out 
that most probably one more species of Spatangoids must occur 
in the Irish Sea even if not yet found there, viz. Echinocardium 
pennatifidum , the larva of which is also unknown. * 1 ) 
During my two sojourns at the Swedish Zoological Station I 
made all efforts to fill the gap in our knowledge of the develop- 
ment of our Spatangoids. Echinocardium flauescens is not at all 
uncommon, Brissopsis hjrifera exceedingly numerous in localities 
near the station, so that sufficient material of these two species 
was available. A considerable number of specimens of the former 
species was examined during the first days of my stay this sum¬ 
mer, but the breeding season was past already (end ofjuly), only 
quite few eggs and a mere trace of sperma still remaining, with 
which nothing could be done. It could only be ascertained from 
the character of the eggs, which are very small and quite trans¬ 
parent, that the species must have pelagic larvæ. The interesting 
question, how far the larva of this species resembles that of 
Echinocardium cordatum in its main features or it is really ident- 
ical with the larva figured by Chadwick, and thus differing quite 
# 
markedly from the Ech. cordatum larva, remains then to be solved. 
‘) After this paper was sent to the press I received from Dr. Chadwick 
a slide with some of the larvæ represented in the figures quoted above. 
I find that the postoral rod is fenestrated in its outer part, as is the case 
in the Brissopsis larva. Unfortunately, the fully developed larvæ men- 
tioned by Chadwick have not been preserved. It cannot, therefore, 
be decided, whether Chadwick’s larvæ belong to Brissopsis or per¬ 
haps to Echinocardium flauescens. 
Vidensk. Medd. fra Dansk naturh. Foren. Bd. 71. 10 
