NOTES AND MEMORANDA. 



Recent researches on the Nervous System of the Medusae. — 



Altliough the reinaikal)le memoir of Dr. Kleineiiberg on Hydra 

 has for some time pointed out to biologists the importance of 

 the study of the Coelenterate nervous system for the solution of 

 questions on the origin of the nervous system, it is not 

 till witiiin the last two years that the subject has been again 

 taken up. Since then the nervous system of the Medusae has 

 formed the subject of a series of researches both on the physio- 

 logical and morphological sides. The very brilliant physiological 

 investigations of Mr. Eoinaiies^ are well known to all naturalists 

 in this country, and we need only call attention in this connection 

 to the investigations carried on simultaneously by Dr. Eimer."^ 

 Prom the morphological side there has appeared a memoir by 

 Professor Claus,^ a very elaborate monograph by the brothers 

 Hertwig/ which completely revolutionizes our knowledge on this 

 subject, and a note by Professor Schafer,^ which, though un- 

 fortunately short and without illustrations, still serves to fill up 

 important lacunae in the more elaborate memoirs of the German 

 naturalists, and is, we trust, only the prelude to a more complete 

 investigation. We propose giving a short account of the 

 morphological results of the investigations relating to Medusae, 

 but more especially those of the brothers Hertvvig. 



The nervous system is difl'erently constituted in the Craspedota 

 and the Acraspeda. We shall commence with the former, for our 

 recent knowledge of which we depend almost entirely on the 

 obserrations of the brothers Ilertwig. The central part of the 



> ' Pliil. Transactions of the Society of London,' 1876 and 1877. 



' " Ueber kunstliche Tlieilbariteit ii. iiber das Nerveiisvst.. d. Meduscn," 

 ' Arcbiv f. Mikr. Anat.,' Bd. xiv. Dr. Eimer has also |jublished an impor- 

 tant memoir on tiie nervous system of licroe, ' Zoologische Untersuciiuiigen,' 

 Wuizburj;^, 1874, of wliich, liowovcr, we do not propose to f,nve an accouht, 



' " Studien ueber Tolypen u. Qualleu d. Ardria." ' Denlw. k. Akad.' W ieu, 

 1877. 



* • Das Nervensystem u. die Sinnesorgane der Medusen,' by 0. Ilertwig 

 and R. licrl-wig. 



'^ Troccedings of Royal Society,' Jan., 1878, No. 185. 



