HETEROMORPHOSIS 119 
repeated and confirmed. I am not in a position to state 
whether they are correct or not. 
The theory given by Bonnet is in some points similar to 
a theory brought forward by Duhamel in his Physique des 
arbres, and to which Sachs goes back in his papers on 
“Stoff und Form der Pflanzenorgane.”' 
Bonnet believes that just as there are specific germs for 
the development of the entire animal, there are also special 
germs for the development of the various organs; he assumes 
the existence of certain head germs and certain tail germs. 
In order, however, that these germs may develop, they must 
be particularly well nourished. Their nutrition is accom- 
plished, as in plants (according to Duhamel), by various 
kinds of saps, one of which serves for the nutrition of the 
head, while the other nourishes the tail. The latter flows 
from head to tail, the former in the reverse direction. If, 
now, the head is cut off, the saps which heretofore served to 
nourish the head, can now be utilized for the nutrition of 
the head germs, and the latter begin to grow out at the cut 
oral end into a new head. In a similar way the tail germs 
may begin to grow when the tail is cut off. It is assumed 
that the tail germs and the head germs are distributed 
evenly throughout the body of the vers rougedtres; for this 
reason a head must always grow from the oral end of a 
fragment cut from any portion of the animal, while the 
aboral end must always give rise to a tail. Upon the other 
hand, in the vers blanchatres the head germs are found 
only in the neighborhood of the head, while the tail germs 
are distributed through the entire body. For this reason 
the worm regenerates a new head when the head is cut off, 
while a new tail is formed at either end when a piece is cut 
out of the middle of the worm.’ 
1Arbeiten des botanischen Instituts in Wurzburg, herausgegeben von SACHS, 
Vol. II (1882), pp. 452 and 689, 
2Cn. Bonnet, Considération sur les corps organisés, Art. 259 ff.; Geuvres (Neu- 
chatel, 1779), Vol. VI, pp. 48 ff. 
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