2022 Journal of Applied Microscopy 



GENERAL PHYSIOLOGY. 



RAYMOND PEARL, University of Michigan. 



Books and Papers for Review should be Sent to Raymond Pearl, Zoological Laboratory, 

 University of Michigan, Ann Arbor, Mich. 



Yerkes, R. M. A Contribution to the Phys- In the first of these papers the author 



iology of the Nervous System of the Medusa , ., •, r n i ,■ /• 



Gonionemus Murbachii; Part I. The Sen- describes quite fully the reactions of 



sory Reactions of Gonionemus. Amer. Jour. Gonionema tO chemical, mechanical and 



y lo • • 434 449. 9 - photic Stimuli. While the tentacles are 



TT A Contribution to the Physiol- ^^e most sensitive portions of the 



ogy of the Nervous System of the Medusa ^ 



Gonionema Murbachii. Part II. The Phys- organism tO all Stimuli, yet all parts of 

 iology of the Central Nervous System. ^^g ^ody with the exception of the 

 Ibid, 7: 181-198, 1902. •' ^ 



exumbrella and the velum are sensitive 



to both mechanical and chemical stimuli. The reactions to stimuli fall into two 

 general classes, called by the author (1) the " feeding reaction " and (2) the 

 " motor reactions," including as the most important subdivision the " locomotor 

 reaction." The "feeding reaction" in its entirety is given only in response to 

 chemical stimuli from substances of a nutritive nature. The reaction consists 

 of a series of coordinated movements of the tentacles, bell and manubrium, 

 which together bring about the carrying of the food substance to the mouth. 

 To harmful substances the " locomotor reaction " is given. This reaction takes 

 the organism quickly away from the harmful stimulus. The ability of the organ- 

 ism to react differentially to different chemical substances (foods and non-foods) 

 indicates the possession of some power of discrimination or choice. The organ- 

 ism is found to be positively photo/ar//V in daylight, and negatively photo/rt'/'///r 

 to daylight and to greater intensities of light. 



The purpose of the second of the papers is to determine the relation of the 

 nervous system of Gonionema to its reactions. The author finds that the reac- 

 tions of special parts or organs of the animal are not dependent on the activity 

 of the central nervous system. Spontaneity is not dependent on the central 

 nervous system, but upon the high degree of irritability of certain parts of the 

 margin of the bell. The marginless bell does not show spontaneity simply 

 because it is insensitive to any stimuli except those of considerable intensity. 

 Yerkes develops a theory of coordination which makes the process independent 

 of the functioning of the nerve ring or any special nerve center. According to 

 the view advanced coordination is dependent simply upon the rapid transmission 

 of an impulse, probably muscular rather than nervous in nature. All the tissues 

 except the jelly and exumbrella are capable of transmitting impulses. 



Together the papers form an important contribution to our knowledge of the 

 behavior of a lower organism on which very little thorough work has previously 

 been done from this point of view. It is to be noted that in the second paper 

 the author, for etymological reasons, changes the generic name Goniomus to 

 Gonionema. r. p. 



