ORGANIZATION AND GROWTH 205 
I shall have to continue the experiments before I can 
discuss the conditions which determine the formation of 
these abnormalities. 
IV. ON THE INTERNAL CAUSES OF ORGANIZATION IN 
TUBULARIA MESEMBRYANTHEMUM 
1. In most animals at a cut edge with a definite orienta- 
tion only one kind of organ originates. If the tail of a 
lizard or a salamander is amputated, only a tail and nota 
head is regenerated in its place, and a lobster develops a new 
pincer in place of the one lost, and never anything else.’ 
Nor can it be said that only the higher animals show this 
inflexibility in organization. As shown by all the experi- 
ments which have been made upon it for a hundred and fifty 
years, Hydra behaves thus; even in Infusoria Nussbaum 
found such a relation to exist between the new growth and 
the orientation of the wound.’ In plant physiology the 
instances in which complete control of organization through 
external forces is possible are very scarce. In the majority 
of these experiments, also, it seems that internal, and at 
present unknown, factors essentially determine the position 
of the organs. If we wish to control these internal con- 
ditions in animals, we must try to obtain further information 
concerning them through experiments. In order to give the 
reader a clearer idea of the réle of these internal causeg in 
animal morphogenesis I will remind him of the experiments 
upon Cerianthus membranaceus, given in the first volume of 
my Physiological Morphology.’ The oral pole a of Cerian- 
thus differs markedly morphologically from the aboral pole 6 
(Fig. 52). To be brief, I will mention only one difference— 
that tentacles arise from the oral pole. Ifa rectangular piece 
1This is no longer correct. Herbst has sbown that in Crustaceans in the place 
of an eye a new eye or a new tentacle can be produced at desire. [1903] 
2M. NussBaum, Archiv ftir mekroskopische Anatomie, Vols. XXVI and XXIX. 
3See Part I, p. 115. 
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