June 12, 1908] 



SCIENCE 



911 



Some Beactions of the Pomace Fly (Dro- 

 sopliila ampelophila) to External Stim- 

 uli: Frederic W. Carpenter, University 

 of Illinois. 



Drosophila is negatively thermotropic 

 to high and low temperatures. In react- 

 ing on a horizontal surface to the tempera- 

 ture stimulus the insect usually describes 

 a continuous curved line, and gives little 

 evidence of random movements indicating 

 "trial and error" behavior. 



Experiments with light have shown that 

 Drosophila is positively phototropic. If 

 one eye is covered with an opaque cap, 

 the insect, in spite of the unilateral stim- 

 ulation, creeps in a fairly direct path 

 toward the light, although often showing a 

 tendency to deviate toward the side of the 

 normal eye. Occasionally a fly will per- 

 form circus movements, but this behavior 

 is exceptional. 



A violent uncoordinated motor reaction 

 or convulsive reflex may be produced by 

 stimulating Drosophila either by a high 

 temperature, or by a low temperature, or 

 by intense light (at a temperature of 30° 

 C.) or by such irritating chemical sub- 

 stances as ammonia or acetic acid. 



Behavior of Perichceta and Lumhricus 

 toward Stimuli of Various Intensities: 

 E. H. Harper, Northwestern University. 

 Stimulation of the anterior end on one 

 side gives reactions of five types cor- 

 responding to the strength of the stimulus. 

 The weak negative reaction of type I. is 

 the terminus likewise of the next two 

 types owing to the gradual subsiding of 

 the stimulus. The medium reaction of 

 type II. is therefore two-phased, retrac- 

 tion of the head being only the first phase. 

 The increased intensity of the first phase 

 in type III. (strong reaction) determines 

 the backward crawling, allowing the pos- 

 terior end to take the lead. The extension 

 of the same strong condition of contraction 



over the posterior end in the very strong 

 reaction of type IV. prevents backward 

 crawling owing to the weaker adaptiveness 

 to backward as compared with forward 

 movements. Strong turning with forward 

 movement is, therefore, the very strong 

 type of reaction. Type V. is a convulsive 

 reaction. Type III. shows three subtypes 

 according to strength of stimulus. Sub- 

 type III. (6) introduces squirming of the 

 anterior end; III. (c) includes a rolling 

 reaction produced by contracting the 

 longitudinal muscle bands in sequence, 

 which follows the squirming and precedes 

 the backward movement. This rolling re- 

 action wipes off the stimulating substance 

 with secreted mucus. As variants may be 

 noted omission of backward crawling from 

 III. (h) and (c). Trial and error is not 

 recognized in this apparently determinate 

 series of reactions, though, as others have 

 noted, the movements of type I. may be 

 random. Of course the same description 

 may be applied to V. 



The Reaction of Amphibian Embryos to 

 Tactile Stimuli: G. E. Coghill, Denison 

 University. 



With reference to the reaction to a tac- 

 tile stimulus upon the region of the tri- 

 geminus or vagus, embryos of Triton toro- 

 sus may be grouped into three classes: (1) 

 Individuals which from the first and dur- 

 ing a considerable period respond regularly 

 or almost regularly with a heterolateral 

 (away from the side touched) head move- 

 ment. (2) Individuals which for a rela- 

 tively short period are irregular in the 

 direction of the head movement and then 

 enter upon a long period of heterolateral 

 reaction. (3) Individuals which are at 

 first asymmetrical in response, then enter 

 upon a short period of irregularity and 

 finally upon a period of heterolateral reac- 

 tion, or pass directly from asymmetry to 

 the heterolateral type. • 



