22 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



interesting information toucliing tlie structure of 

 the sense-organs in various species of Medusae ; 

 but it seems scarcely necessary to extend the 

 j)resent resume of their work by entering into this 

 division of their subject. 



In a later publication, entitled " Der Organismus 

 der Medusen und seine Stellung zur Keimbliitter- 

 theorie," Drs. Hertwig treat of sundry features in 

 the morphology of the Medusae which are of great 

 theoretical importance ; but here again it would 

 unduly extend the limits of the present treatise if 

 I were to include all the ground which has been 

 so ably cultivated by these industrious workei's. 



It will presently be seen in how striking a 

 manner all the microscopical observations to which 

 I have now briefly alluded are confirmed by the 

 physiological observations — or, more correctly, I 

 might say that the microscopical observations, in so 

 far as they were concerned with demonstrating the 

 existence of nerve-tissue in the Medusae, were fore- 

 stalled by these physiological experiments ; for, with 

 the exception of Professor Haeckel's work on 

 Geryonidtie, they were all of later publication. But 

 in matters of scientific inquiry mere priority is not of 

 so much importance as it is too often supposed to be. 

 Thus, in the present instance, no one of the workers 

 was in any way assisted by the publications of 

 another. In each case the work was independent 

 and almost simultaneous. 



The remark just made applies also to the only 

 research which still remains to be mentioned. This 

 is the investigation undertaken and published by 



