1897.] MR. E. T. BEOWyE ON BEfTISH MEDUS.E. 825 



from generative cells. The gouads in all the specimens were quite 

 colourless. 



The margin of the umbrella is thicklv beset with I0112 tentacles, 

 the number varying according to the size of the umbrella, as shown 

 by the following examples : — • 



The tentacles first make their appearance as bulbs on the inner 

 side of the margin, which is fairly broad. The bulb apparently 

 grows outwards across the margin, and the tentacles develop from 

 the outer end of the bulb. The tentacle gradually tapers from 

 the bulb ; it is at least 25 mm. in length, when expanded, and 

 covered with nematocysts. The attachment of the tentacle to the 

 umbrella is further strengthened by an outgrowth which extends 

 from the bass of the tentacle for a short distance along the e.\- 

 umbrella. The outgrowth is usually triangular in shape and con- 

 sists of large cells. Tliis outgrowth or " spur " appears after the 

 development of the tentacle, and is absent or scarcely visible in 

 young stages. 



When the medusa is motionless in an aquarium, the tentacles are 

 arranged in two positions. The basal portion of one tentacle 

 points upwards, and that of the adjacent one slopes slightly down- 

 wards ; the basal portion is stiff and straight, the outer portion 

 gracefully curves over, with the free end hanging down and 

 tapering out to an almost invisible thread. On the inner side of 

 the basal bulbs of the tentacles, and just below the ring-canal, 

 there is usually situated a black ocellus. The ocelli show a con- 

 siderable amount of variation in number. As a rule there is not 

 one opposite every tentacle, but every alternate tentacle. In 

 the same individual several adjacent tentacles may each have an 

 ocellus at their base, then an alrernating series, one with, and the 

 next without an ocellus ; and followed by two or three adjacent 

 tentacles without ocelli. In one large specimen I counted 228 

 tentacles, but only 88 ocelli, and in another large specimen I 

 noticed an ocellus opposite nearly every tentacle. 



On the inner side of the margin of the umbrella are situated 

 the curious sensory clubs or cordyli — one about midway beween 

 every two tentacles ; they usually point inwards, and lis close to 

 and below the velum. Brooks has recently given a description 

 and figures of these organs. 



In addition to the tentacles and cordyli there are also long fili- 

 form cirri, armed with nematocysts : usually one between every 

 two tentacles, but often two are present, and are situated close 

 to the bulb of the tentacle. In a few specimens I noticed that a 



Pboc, Zool. Soc— 1897, No. LY. 55 



