86 INHERITANCE IN SILKWORMS, I 



isolated scent-glands as they are to unmutilated females ; on the contrary they 

 are not at all attracted to the mutilated females. If the cut-out scent-glands are 

 put by the side of and but a little apart from the female from which they are 

 taken, the males always neglect the near-by live female and go directly to the 

 scent-glands. Males attracted to the isolated scent-glands remain by them per- 

 sistently trying to copulate with them, moving excitedly around and around them 

 and over and over them with the external genitalia vainly trying to seize them. 



The behavior of males with the antenna of only one side removed is strik- 

 ing. A male with left antenna off when within three or four inches of a female 

 (with protruded scent-glands) becomes strongly excited and moves energetically 

 around in repeated circles to the right, or rather in a flat spiral thus getting 

 (usually) gradually nearer and nearer the female and finally coming into con- 

 tact with her, when he is immediately controlled by the contact stimulus. A 

 male with right antenna off circles or spirals to the left. It is a curious sight 

 to see two males with right and left antenna off, respectively, circling violently 

 about in opposite directions when he immobile female a few inches removed 

 protrudes her scent-glands. This behavior is quite in accordance with Loeb's 

 explanation of the forward movement of bilaterally symmetrical animals. 



The results of all the experiments tried show how rigorously the male 

 moths are controlled by the scent attraction (chemotropism) and how abso- 

 lutely dependent mating (the one adult performance of the males) is on this 

 reaction. If we can find specialized animals in a condition where all attractions 

 and repulsions (stimuli) but one are eliminated we may readily perceive the 

 rigorous control exercised by this remaining one. We are, unfortunately, in 

 the general circumstances of animal life too much limited to the use of very 

 simply organized animals for reaction and reflex experimentation. This tends 

 to make it difficult to carry over to the behavior of complexly organized animals 

 the physico-chemical interpretation which is steadily gaining ground as the key 

 to the understanding of the springs and character of the behavior of the simplest 

 organisms. But where the complex stimuli and reactions that determine the 

 behavior of complexly organized forms can be isolated and studied the inevitable- 

 ness of much of this behavior can be recognized. 



Reflexes of Moths Without Cephalic and Thoracic Ganglia. — A number of 

 experiments was made to determine the need, or absence of need, of the principal 

 ganglia of the central nervous system in the performance of the two chief reflexes 

 in the silkworm moth's life, viz., mating and egg-laying. 



Males mate with headless females, and the headless females, after mating, 

 lay a few eggs which develop normally, that is become fertilized by the release 

 of spermatozoa from the spermatheca in the female's body, are oviposited by the 

 repeated extrusion and retraction of the ovipositor, and make the usual color 

 changes (from yellow to cherry-red and then to lead-gray) incidental to normal 

 development. But in no case did a headless female lay her full complement of 

 eggs, in fact in no case were more than a score of eggs laid (the normal number 

 is from 200 to 350). Headless females (and headless males) usually live as 

 long as unmutilated individuals, i. e., from a week to two weeks. 



Females with head and thorax cut off (and even part of the abdomen) can 

 be mated with by males, and this fractional part of the female can fertilize 



