THE NERVOUS SYSTEM IN GONIONEMA 



MURBACHII. 



IDA H.'HVDE. 



Some physiological work which I undertook this summer at 

 the Woods Hole Biological Laboratory on the Hydromedusa, 

 Gonionema Murbachii, made it important that I should know the 

 distribution of its nervous system which at the time had not been 

 described or known with certainty. I decided, therefore, to gain 

 some knowledge of the distribution of its nerves by means of 

 Bethe's methylene-blue method. Inasmuch as my time for this 

 work at Woods Hole was very limited, I was unable to under- 

 take an exhaustive histological study of the whole nervous system 

 of the medusa. Believing it of some interest to make known the 

 facts that were obtained, it was decided to publish them in a brief 

 preliminary report, hoping in the near future to see the subject 

 completed by Mr. Chas. G. Rogers who has consented to make 

 a detailed histological study of the distribution of the nerves, in 

 connection with some work which he is pursuing on regeneration 

 in this animal, under the direction of Dr. Loeb. 



All my observations were made on fresh material. The whole 

 or small parts of the animal were exposed six or more hours to 

 the action of a weak sea-water solution of Bx methylene blue 

 freshly made and filtered for each study. The material was kept 

 in a cool place and transferred for study from methylene blue to 

 sea-water or a i;i/S solution of sodium chloride. Some material 

 was kept for future study as long as twenty-four hours on ice in 

 10 per cent, ammonium molybdate to which a few drops of I per 

 cent, osmic acid and hydrogen peroxide had been added (i gm. 

 ammonium molybdate, loc.c. distilled water, i c.c. hydrogen per- 

 oxide, two drops i per cent, osmic acid). 



Small pieces were dissected from different regions and examined 

 ,with an oil immersion lens. The study of these sections dis- 

 closed, besides the double nerve ring around the margin ; usually 

 designated as the central nervous system, a third ill-defined very 



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