AUTOTOMY IN HOLOTHURIANS.^ 



A. S. PEARSE. 



I. Introduction. 



It seems remarkable that any animal should make a regular 

 practice of casting off parts of its body, and it is not strange that 

 autotomy has long been a subject of more than passing interest 

 to the scientific world. Although this phenomenon is present in 

 a variety of animals it has been most fully studied in the arthro- 

 pods and echinoderms. In the first of these groups the nervous 

 control of the reflexes concerned has been investigated (Drzewina, 

 : 07 ; Morgan, : 02), and there seems to be no doubt that autotomy 

 may occur as a result of stimulation which exerts no direct me- 

 chanical strain on the parts thrown off (Torre Bueno, : 08). It 

 is even maintained to be a psychic phenomenon in some cases 

 (Pieron, : 07) which is due to conditions within the animal itself. 

 Many echinoderms are known to break off portions of the body 

 as a result of external stimulation (Lang, '96), but, to my 

 knowledge, no studies directly concerned with the nervous con- 

 trol of such reactions have been made. 



The experiments described in this paper were performed upon 

 the two common holothurians which are found at Woods Hole, 

 Leptosynapta inhcerens (O. F. Miiller) and Thyoiie briareus 

 (Leseur). The object of the work was to discover the relation- 

 ship of the central nervous system to the reflexes involved in 

 autotomy. Evidence was obtained in two different ways. In 

 one method of experiment various chemicals were injected into 

 the body cavity, and their effect upon the general behavior of the 

 animal was observed in connection with the phenomenon of self- 

 mutilation. In another series of experiments animals were cut in 

 two and the subsequent reactions of the two ends were compared. 

 In this way evidence as to the importance of the nerve ring was 

 obtained. 



1 Contributions from the Zoological Laboratory of the University of Michigan, No. 

 127. 



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