150 
V. Antedon petasus (Duben & Koren). 
It might be expected beforehand that the development of this 
species would present no essential differences from that of its near 
relatives: Antedon bifida, mediterranea and adriatica , the latter 
of which species has been so very carefully studied by Seel i ger, 
and is in the text books made the typical representative of Crin- 
oid development upon the whole. Having, however, through my 
researches on the development of the West Indian Crinoid Tropio- 
metra carinata, 1 ) found that quite essential differences may occur 
in regard to development in Comatulids, I thought it well worth 
while to study the development also of Antedon petasus and to 
ascertain how closely it would agree with the other species of 
Antedon s. str. The result was, indeed, rather suprising. 
The breeding season of Antedon petasus is mainly in August and 
September; ripe specimens were, however, found already on the 
23rd of July 1919, and that breeding may take place until rather 
late in the autumn is evident from the faet that I found in Jan- 
uary 1910 a Pentacrinoid not yet fully ready to detach itself from 
the stalk. 2 ) 
I naturally expected to find the eggs and young embryos at- 
tached to the pinnules in the same way as in the other spec¬ 
ies of Antedon which have been studied hitherto as regards 
their development. A great number of specimens were carefully 
examined, but without success; there was never to be found a 
specimen with eggs round the genital openings. Although I could 
hardly believe it possible, I was then forced to the idea that the 
eggs might be free as in Tropiometra. The bottom of the dishes 
and aquaria in which the specimens were kept was examined and 
there the eggs were found lying. The surprising faet was thus 
ascertained (and reascertained many times since) that Antedon 
*) A full report on these researches, together with observations on the 
development of some other Crinoids is given in a memoir: Studies in 
the development of Crinoids, which will appear in Papers from the De¬ 
partment of Marine Biology of the Carnegie Institution, Washington, 
Vol. XVI. 
3 ) T h. M o rte n s e n. Report on the Echinoderms coll. by the Danmark 
Expedition at North East Greenland. (Medd. om Grønland. XLV. 1910. 
p. 250. PI. X. Fig. 3). 
