22 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
interesting information touching the structure of 
the sense-organs in various species of Medusze ; 
but it seems scarcely necessary to extend the 
present réswmé of their work by entering into this 
division of their subject. 
In a later publication, entitled “ Der Organismus 
der Medusen und seine Stellung zur Keimblatter- 
theorie,” Drs. Hertwig treat of sundry features in 
the morphology of the Medusze 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 workers. 
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 Medusz, were fore- 
stalled by these physiological experiments ; for, with 
the exception of Professor Haeckel’s work on 
Geryonide, 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 
