TRANSFORMATION or 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 of. of 

 NaCl had been added to each 100 c.c. of sea- water. After 

 the detailed description of the behavior of the Polygordius 

 larvae 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: 1 



When I had [Haematococcus] 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 Hsemato- 

 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 Hsematococcus swarm spores and Poly- 

 gordius larva? and Copepods. I consider it possible that 

 animals may be found which become negatively heliotropic 

 when cooled. Massart 2 found similar phenomena in Flagel- 



1 Jena, 1878, p. 56. 



2 JEAN MASSART, Bulletin de I ' Academic royale de Belye, V< .1. XXII (1891). 



