206 JELLY-FISH, STAR-FISH, AND SEA-URCHINS, 
interesting character to describe, which is closely 
connected with the current views respecting gan- 
glionie action, and may therefore be more con- 
veniently considered here than in any other part of 
this treatise. I have already stated that in no case 
is the manubrium of a Medusa affected as to its 
movements by removal of the periphery of the 
swimming-bell; but in the case of Sarsia a very 
interesting change occurs in the manubrium soon 
after the nectocalyx has been paralyzed by excision 
of its margin. Unlike the manubriums of most of 
the other Meduse, this organ, in the case of Sarsia, 
is very highly retractile. In fresh and lively speci- 
mens the appendage in question is carried in its 
retracted state; but when the animals become less 
vigorous—from the warmth or impurity of the 
water in which they are confined, or from any 
other cause —their manubriums usually become 
relaxed. The relaxation may show itself in various 
degrees in different specimens subjected to the same 
conditions, but in no case is the degree of relaxa- 
tion so remarkable as that which may be caused 
by removing the periphery of the nectocalyx. For 
the purpose of showing this effect, it does not 
signify in what condition as to vigour, etc, the 
specimen chosen happens to be in; for whether 
the manubrium prior to the operation be contracted 
or partially relaxed, within half an hour after the 
operation it is sure to become lengthened to a 
considerable extent. 
In order to show the surprising degree to which 
this relaxation may proceed, I insert a sketch of a 
