THE BEHAVIOR OF THE LOWER INVERTEBRATES 399 



Following a description of the eye-spot of Gonium pectorale, 

 Mast (20) gives an account of the process of orientation to light 

 in this organism. Orientation is direct (the colonies never 

 turning in the wrong direction) and in positive colonies it is 

 brought about by an increase in the activity of the flagella of 

 the 7ooids on the side away from the light. This is held to 

 be dependent upon the time-rate of change of illumination on 

 the tissue which is sensitive to light. 



Mast and Lashley (21) find that there is no continuous pro- 

 duction of a feeding-cone in free-swimming Paramoecia, Stentor 

 or Spirostomum. The water sucked toward them is through 

 so short a distance (probably not over twice the length of the 

 cilia) as to make such currents of no appreciable value in test- 

 ing unfavorable environment ahead of the specimen. The 

 feeding-cone is produced only under special conditions. 



Mast and Root (22, 23) find that the pseudopods of Amoeba 

 proteus in forming a food vacuole about a Paramoecium some- 

 times come together before they are fully extended, thus cutting 

 the latter in two. The authors estimate that if this process is 

 due solely to a change in the surface tension on the surface of 

 the Amoeba it would have to be higher than 383 dynes per 

 cm. * at the very least and that it probably would have to exceed 

 1,118 dynes per cm. J As the surface tension of protoplasm is 

 only about 50 dynes per cm. 2 , they conclude that if surface ten- 

 sion plays a part in the division of Paramoecium it is a very 

 insignificant role. 



Maupas and Seurat (24) give a note on the copulation of 

 certain nematodes. 



As a result of a study of certain reactions of Cassiopea xana- 

 chana, Mayer (25, 26, 27) gives some interesting suggestions as 

 to the nature of nerve conduction in this organism. 



Mendelssohn (28) finds that a leucocyte, in response to the 

 stimulation of an electrical current, so changes its form as to 

 produce one large pseudopodium which is always directed 

 towards the cathode. 



Metalnikov (29, 30) finds that the length'of- time that a given 

 food vacuole will circulate in the body of Paramoecium is very 

 variable. According to him this variability depends upon three 

 factors: (1) The character of the specific stimulating substance, 



