478 MB. B. 1\ BEOWNB ON [Mar. 17, 



Agassiz (1865) has described a medus{i,Lizziaffratci(=MargelUum 

 gratwn, Haeckel), which has five tentacles iu each of the four 

 pei'radial groups and three tentacles iu each of the four interradial 

 groups. Erom the specimens collected at Valencia, I have every 

 reason for believing that Lizzia (/rata is the adult form of 

 Margellium octopunctatum. 



The early stages of Mart/ellmm octopunctaiiim vi'ere fairly 

 abundant in Valencia Harbour at the beginning of April, but 

 decreased iu number during May. Most of the specimens taken 

 during April and the early part of May had one to four 

 medusa-buds upon the stomach. About the middle of May 

 specimens were taken with either ova or spermatozoa upon the 

 wall of the stomach. The reproductive cells first begin to appear 

 upon the perradial ridges on the outside wall of the stomach, and 

 aa they increase in size they form a mass covering the wall of the 

 stomach. As soon as the reproductive cells begin to appear, the 

 budding of medusae ceases. The compound basal bulbs of the 

 tentacles show little variation in colour, being usually dark brown 

 or black. One specimen, however, had reddish-brown bulbs. 



The specimens taken at Valencia resemble those taken at Port 

 Erin. I have no doubt that they belong to the same species, and 

 as they were taken in a distant locality it may be of interest to 

 record some for comparison with those taken at Port Erin. The 

 following list shows the number of tentacles in each perradial and 

 interradial group of 16 specimens taken at Valencia. It is also 

 arranged to show the increase in the number of tentacles during 

 the growth of the medusa. 



Perradial 3333 3333 3333 3333 3333 8334 

 Interradial llTa' 3231' 2222' 2333' 3333' 3333' 



Perradial 4343 5334 5344 5433 5444 4454 

 Interradial 3333' 3333' 3333' 3333' 3333' 3333' 



Perradial 5454 5553 5554 5555 

 Interradial 3333' 3333' 3333' 3333" 



The above series corresponds very closely with a series given in 

 the lleport on the Isle of Man Medusas. 



The umbrella of the earliest stage is about 1 mm. in length, and 

 that of the adult from 3 to 4 mm. 



Not only does the medusa increase the number of its tentacles 

 as it grows, but also the number of clusters of nematocysts upon 

 the oral tentacles, which are four in number. Though some of the 

 specimens taken off the Isle of Man possessed the same number 

 of tentacles as Margellium gratum, the clusters of nematocysts 

 upon the oral tentacles were fewer in number. Until I had seen 

 an exact similarity in every detail, I did not feel justified in placing 

 Margellium gratum as the adult of Margellium ociopunctatum. At 

 Valencia I specially examined the oral tentacles of every specimen 



