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younger specimens from the free (e. g. in the very characteristic 
structure of the disk plates) so that there could be no doubt that 
the Ophiurid reared from Ophiopluteus mancus was 
really an Amphiura. 
Although the experiment was not carried on until the full re¬ 
sult was reached (the appearance of the infradental papillæ) it is 
evident that here we have a method which may be used with 
success in the study of the postembryonal development of Ophiu- 
rids, and doubtless also of other Echinoderms. Experiments were 
made likewise with metamorphosing larvæ of Ophiura albida ; also 
in this case the metamorphosis went on normally in iarvæ kept 
in separate dishes and the young Ophiurids grew to some size; I 
did not, however, take special care to carry this experiment further. 
— It is worth mentioning that in the aquarium with the Amphiura- 
culture there proved to have developed an astonishing number of . 
Foraminifera; also a great number of Nematods had developed. 
Though it was thus proved that Ophiopluteus mancus is the 
larva of Amphiura , the question still remained undecided to which 
of the two species A. filiformis or Chiajei it should be referred, 
as I found it impossible to distinguish these two species in the 
very young stages. During my visit to the Station at Kristineberg 
this summer (1919) I made therefore renewed efforts to solve the 
question, trying this time especially to get the Amphiuras to shed 
their eggs in the aquaria and thus to be able to rear the larva from 
the egg. From the material taken by dredging such specimens were 
carefully selected which were full of apparently ripe sexual products 
(in Amphiura filiformis with its transparent skin on the ventral 
side of the disk this is very easily seen) and otherwise unhurt 
and in good condition. A number of such specimens, the two spec¬ 
ies kept separately, of course, were put into aquaria with sifted mud 
from the locality where they were dredged. They lived there ex¬ 
cellently, especially A. filiformis , lying — in the well known way 
— buried in the mud with only the points of the arms rising over 
the surface of the mud, catching eagerly the food (pieces of mus- 
sels, Crustaceans) put before them. After two or three days (on 
August 12th) I had the great satisfaction of seeing them discharge 
their sexual products. The way in which it was done was rather 
surprising and deserves a more detailed description. 
