70 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
[ have failed to procure any results from crossing M. norvegicus 
with M. rattus. I think no result has ever yet been obtained. 
My results from crossing M. r. rattus (Black Rat) with both 
M. r. alexandrinus and M. r. frugivorus have been successful, 
producmg about an equal number of each colour, with this 
exception. The pair, Black male M. r. rattus and Brown dark 
bellied female M. r. alecandrinus, produced one white-belhed 
brown M. r. frugworus in each litter. 
Dr. Bonhote found on crossing M. r. frugiworus with M. r. 
alexandrinus that the former was apparently a simple mendelian 
dominant to the latter. 
The experiment of de L’Isle seem to indicate that M. r. 
rattus behaves in turn similarly as a dominant to M. r. 
frugworus. : 
Morgan’s experiments (American Naturalist, 1909) showed 
that which ever way the cross was made the progeny ot Mow: 
frugworus < M. r. rattus were black. 
Hagedoorn (American Naturalist, 1917) found that the 
Black M. r. rattus behaves as a simple dominant. 
My experiment is now in the Mendelian stage F. 2. I hope 
to publish the results later. 
