TRANSFORMATION OF HELIOTROPIC ANIMALS 283 
become positively heliotropic. Later, when the temperature 
again rose, they again became negatively heliotropic 
The addition of 80 parts of fresh water to 100 parts of 
normal sea-water made positively heliotropic Copepods nega- 
tively heliotropic; the addition of 60 per cent. of fresh water 
made a number of them negative, and a smaller addition 
had little or no effect. 
Almost all negative Copepods became positively helio- 
tropic when introduced into sea-water to which 1.5 g. of 
NaCl had been added to each 100 c.c. of sea-water. After 
the detailed description of the behavior of the Polygordius 
larve these statements may suffice. 
7. I have already shown in my earlier papers on heliot- 
ropism that there is scarcely a heliotropic reaction in plants 
which cannot also be demonstrated in animals. This fact is 
again corroborated by the phenomena which we have de- 
scribed here. I quote the following from Strassburger’s 
well-known investigation on the effect of light and heat 
upon swarm spores:' 
When I had [Heematococcus] swarm spores before me which 
had collected, at the ordinary temperature of the room in which 
I worked (16-18° C.) at the positive edge of the drop, I was sure of 
being able to transfer them to the negative side of the drop, at the 
same light intensity, when I exposed the preparation to a tempera- 
ture of about 4° C. At this low temperature almost all of them 
went to the negative edge of the drop. On the other hand, I was 
almost as certain to find the most negatively heliotropic Hemato- 
coccus swarm spores at the positive edge of the drop when I 
exposed the preparation to a temperature of about 35° C. 
Only in the sign of heliotropism is there a difference in’ 
the effect of heat on Hematococcus swarm spores and Poly- 
gordius larvee and Copepods. I consider it possible that 
animals may be found which become negatively heliotropic 
when cooled. Massart’ found similar phenomena in Flagel- 
1 Jena, 1878, p. 56. 
2 Jean Massart, Bulletin de l’ Académie royale de Belge, Vol. XXII (1891). 
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