VAKIATION IN A JELLYFISH. 



1055 



Such branched or bifurcated tentacles have been recorded pre- 

 viously by several authors, among whom Agassiz and Woodwortli 

 [2] have described the phenomenon in medusae of Ohelia {E acope) , 

 and Hargitt [8] came across a similarly abnormal specimen of 

 Gonionemus. 



It seems highly probable that such abnormalities are not 

 congenital, these bifurcated tentacles having no doubt arisen as 

 the result of injury to normal ones, 



Text-fi^. 228. 



Abnoniiiil medusa in wliicli the apical canal is retained. 



The abnormality presented by the other two meditsse is of 

 greater systematic interest : each of these specimens possesses a 

 well-developed apical canal which projects from the base of the 

 stomach into the jelly at the summit of the umbrella (text- 

 fig, 228). This peculiarity is obviously due to the fact that_ these 

 specimens have retained the greater part of the canal which in 

 early life connected the cavity of the medusa-bud with that of the 

 parent-hydroid. 



The presence of an apical canal was at one time considered to 

 be a specific charactei' of some importance, bvit recent systematists * 

 have shown that such a canal occurs frequently as an individual 

 variation in many species which normally lose this organ in the 

 adult stage. 



List of References^; 



1. BouLENGER, C. L.—" On i¥ce?'m« Z?/o?m, a neAv Hydromedusan 

 from Lake Qurun." Quart. Journ. Micr. Sci,, vol. lii. 1908, 

 pp. 357-378, 



* Gf. Mayer's remarks on Sarsia prolifera, and other species of this genus (10). 



t This list includes only those memoirs actually referred to in the text of this 

 paper; for a more complete bibliography I must refer the nader to Dr. Major's 

 recently published monograph (10). 



