SECTION OF NAKED-EYED MEDUSAE. 125 



the usual response to muscular irritation being an 

 ordinary locomotor contraction, which forms a 

 marked contrast to the tonic spasm that invariably 

 ensues upon stimulation of the margin, and almost 

 invariably upon the stimulation of a radial tube. 



The first question I undertook to answer was the 

 amount of section which the excitable tissues of 

 Staurophora laciniata would endure without losing 

 their power of conducting the spasmodic contraction 

 from one of their parts to another. This was a 

 very interesting question to settle, because Stauro- 

 phora laciniata, like all the other species of disco- 

 phorus naked-eyed Medusre, differs from Aurelia, 

 etc., in that the ordinary contraction- waves are very 

 easily blocked by section. It therefore became in- 

 teresting to ascertain whether or not the wave of 

 spasm admitted of being blocked as easily. First, 

 then, as regard* the margin. If this be all cut off in 

 a continuous strip, with the exception of one end 

 left attached in situ, irritation of any part of the 

 almost severed strip will cause a responsive spasm 

 of the bell, so soon as the wave of stimulation has 

 time to reach the latter. I next continued this form 

 of section into the contractile tissues themselves, 

 carrying the incision round and round the bell in 

 the form of a spiral, as represented in the case of 

 Aurelia by Fig. 11, page 70. In this way I con- 

 verted the whole Medusa into a ribbon-shaped piece 

 of tissue ; * and on now stimulating the marginal 



* It may be stated that while conducting this mode of section 

 of Staurophora laciniata, the animal responds to each cut of the 

 contractile tissues with a locomotor contraction (or it may not 



