60 
few cases reported of supposed natural hybrids of Echinoderms are 
of quite recent date. 
The first allusion to the possible existence of natural hybrids 
of Echinoderms was made by A. Ag as s i z. I 11 his „Note sur la 
fertilisation artificielle de deux espéces detoiles de mer“ (Arch. 
Zool. expér. & genér. III. 1874, p. XLVI) he says he found 
several specimens of Asterias berylinus and pallidus (of which two 
species he succeeded in rearing hybrids „jusq’au commencement 
de la formation de l’étoile sur le tube aquifére de la Brachiolaire“) 
which had no sexual products developed at the season when these 
species normally have ripe sexual products. This shows „ou bien 
que les étoiles de mer ne pondent pas annuellement et a la mérae 
saison . . . . ou bien qu’il y a un grand nombre d’Hybrides dans 
les deux espéces, dont les organes génitaux n’atteignent jamais la 
maturité ou seulement rarement“. The question is, however, not 
treated in a more detailed manner, and no description is given of 
the supposed hybrids. 
Quite reccntly a supposed hybrid of Asterids has been described 
by Kalischewskij (Zur Kenntnis der Echinodermenfauna des 
Sibirischen Eismeeres) 1 ). It is named Asterias groenlandica (Steen- 
strup) varietas longimana Kalisch., but the description ends thus: 
„Es ist iiberhaupt leicht moglich dass dieses Exemplar ein Bastard 
zwischen Asterias groenlandica (Steenstrup) and Asterias hyperborea 
Danielssen et Koren ist“. I do not venture to judge of this case 
myself; but since both A. groenlandica and hyperborea are very 
variable and perhaps even represent only varieties of A. Mulleri 
Sars, the suggestion that the specimen described by Kalische wskij 
is a hybrid between the two forms seems to me somewhat 
problematic. 
While no cases of natural hybrids have been described — so 
far as I know — among Ophiurids, Holothurids or Crinoids, some 
few cases of Echinoid-hybrids have been recorded. It may prove 
*) Mém. Acad. Imp. Sc. St. Petersborg. 8 Ser. XVIII. Nr. 4. 1907, 
p. 41. Tab. I. Fig. 10 a-b. Tab II. Fig. 8 a-b. 
