1897] FUNDAMENTAL PRINCIPLES OF HEREDITY 239 
Reviewing the facts, we find that 
(i.) In Protista, each cell retains the power of reproducing in 
its offspring its own characters or those of a direct ancestral cell, 
which we may term the law of direct cellular transmission 
uninterrupted or alternating, according as only one or several 
alternating modes of cellular reproduction constitute the genetic 
cycle. 
(ii.) In Metazoa, the power of reproducing a complete organism 
is confined to certain reproductive cells, which must beget in their 
progeny cells like those which are only related to them collaterally ; 
this we call the law of collateral cellular transmission. 
(ui.) The remaining cells of the Metazoan can seldom or never 
revert closely enough to a primitive type to produce all those other 
tissues of which they are collaterals, though their propagative power 
may be very great. This limitation of reproductive power we may 
call the law of specialised sterility. 
(iv.) In most cases of animal budding or repair we find that the 
several tissues co-operate to produce a complete organism; this we 
call the law of co-operative propagation. 
Marcus Harvoa. 
(To be continued.) 
