EXPERIMENTAL HYBRIDISATION. 
325 
The Experimental Hybridisation of Echinus 
miliaris, Echinus esculentus, and 
Echinus acutus. 
By 
O. Debaisieux, 
Assistant in Zoology at the Univetsity of Louvain (Belgiiiin). 
From tlie Imperial College of Science and Technology, London. 
With Plate 16. 
Tiie few experiments on the hybridisation of the Echino- 
derms of wliich I am now giving the results were commenced 
on the advice of Professor ivIacBride, who himself had made 
similar experiments on other species. At his suggestion I 
chose Echinus miliaris, Echinus esculentus and 
Echinus acutus, in order to verify the interesting results 
obtained by Shearer, De Morgan and Fuchs (’ll) in their 
experiments on these species. I should like in the first place 
to express my thanks to Professor Sedgwick, who so kindly 
received me at his institute, and to Professor MacBride, who 
has helped me so much by his valuable advice and has placed 
at my disposal material whicli he had himself collected. 
The very numerous researches which have already been 
made in the hybridisation of the Echinoderm of various species 
have given results which appear to be very varied. Boveri 
(’89 and ’95) in his crossings of Sphmrechinus and Echinus, 
remarks that the characters of hybrids are mixed and inter- 
