44 
THE ORGANIC CELL 
equal agility. The larval forms of Echinus and Sphcerechinus 
are very different in shape, and after a couple of days’ develop- 
ment can be recognised with great ease. 
A. Dwarf arising from an Enucleated egg fragment of Sphcer echinus 
granulans, fertilised with spermatozoon of Echinus microtuberculatus, and 
showing purely paternal characters. B. Normal Echinus microtuberculatus, 
Boveri. It will be seen they are practically identical except as regards size. 
Having made quite sure of these facts, Boveri cross-fertilised 
the eggs of Sphcerechinus with the sperm of Echinus. The 
