155 
near allies, Antedon mediterranea , adriatica and bifida, that one 
cannot help suggesting that the relation of A. petasus to those 
species may not be so close after all, and that it may perhaps 
not rightly be referred to the same genus. This is, however, not 
the place to discuss this question. — In any case, it has been 
shown that we have here another instance of unexpected great 
diversity in fundamental developmental processes in related forms, 
a striking illustration of the danger in generalizing from a single 
case, as it has been done especially in the case of Crinoids, Ante¬ 
don adriatica being generally taken to represent the type of the 
development in Crinoids upon the whole. — A full report on the 
development of this species would be of the greatest interest. Un- 
9 
fortunately the material available does not suffice for doing so. 
While in the normal development the egg undergoes a total, 
regular cleavage, a curious abnormal modus of development is only 
too commonly observed in the cultures, viz. that only the nuclei 
divide, lying free in the egg substance, which does not show any 
indication of cell limits, forming thus a syncytium. There may be 
found quite a number of nuclei lying in a fairly regular layer near 
the surface, and in later stages also some in the inner part of the 
egg. The develocment, however, does not go any farther, and the 
eggs die off. 
There can be no doubt that this abnormal development is due 
to the unnatural conditions of the aquaria and most probably to 
the too high temperature, so that by future researches it would 
be advisable to keep the cultures at a lower temperature, corres- 
ponding to that normally occurring at the depth, where Antedon 
lives. A quite analogous case is described for Cucumaria fron- 
dosa by Des Arts; 1 ) moreover it was observed for Antedon as 
well as for Cucumaria that a partial disintegration of the egg may 
take place, the rest developing into a pygmæ larva. 
The abnormal development described above recalls that which 
I have found to occur normally in another Crinoid, Isometra vini- 
para, a detailed description of which will be found in the memoir 
referred to above. Also in a number of other Echinoderms I have 
x ) Louis des Arts. Ober die ersten Entwicklungsstadien von Cucu¬ 
maria frondosa unter Beriicksichtigung einiger anormaler Verhåltnisse. 
Bergens Museums Årbok. 1910. No. 13. 
