1892.] Recent Literature. 405 



Though Dr. Loeb's experiments have been for the most pari made 

 upon insects, yet he states that he has been able to demonstrate helio- 



tropism identical with thai of plants in frogs, white mice, (Inmmaru* 

 loewtta, Cttmn rathkii, slugs, planarians, earthwoi ins, leeches, and 



Apparently the experiments of Romanes upon echinodenns are 

 entirely unknown to him. 



In this connection two other contributions to the subject of animal 

 heliotropism, both by Dr. Loeb, may be reviewed as extending the 

 observed tacts over a wider field. 



Groom and Loeb 1 found by direct experiment upon the larva-, 

 nauplius, of a barnacle, that these animals swim towards or away 

 from the light, following the direction of the light and not going 

 towards the more intense light. Moreover, here as elsewhere, it is the 

 more refrangible rays which are most potent. 



negative but are interchangeable in any one individual, so that after 

 the larvae have been in the dark some time they are all positively 

 heliotro pic, but when exposed to the light and moving towards it tor 

 some time they become, some sooner than others, negatively heliotro- 

 pic and swim away from the light, 



This alternation" of effect in the i 

 the authors to the explanation of s 

 position of pelagic organisms, their wandering to and from the surface 

 of the -sea. 



In another paper 2 Loeb shows by experiment upon the large annelid 

 Spirograph!* spallanz.mu that here also the annelid turns towards the 

 source of light, placing its body so that the axis of its somewhat 

 umbrella shaped expansion of radiating branchial plumes coincides 

 with the direction of light. Now as the animal is a sedentary annelid 

 living in a stout leathery tube from which only the branchial and 

 anterior end protrude, this tendency to point to the light is resisted by 

 the elasticity of the tube. 



The tube however is found to bend also, after some time, so as to 

 incline one way or another according to the direction of light, and then 

 remain permanently bent for months, in fact when the animal is 

 removed the tube is still bent. 



