Variations Among ScyphomeduscB. 549 



more or less perfect correlation among the several variable organs 

 of the medusa, but also cites and figures an exceptional case in 

 Taf. II, Fig. 12, in which in a rare octamerous specimen there were 

 found fourteen rhopalia and twenty-eight principal canals, instead 

 of sixteen and thirty-two respectively, as required to complete 

 the symmetry. According to this author the ratio of variation 

 was estimated as about lo per cent (though Agassiz in a following 

 quotation seems to have overlooked this point in Ehrenberg's 

 work). It is not specified as to a hether this includes the totality 

 of variations, or refers to those of the vegetative organs. If the 

 former it was probably too low; if the latter probably too high, 

 as will be seen in the following data : 



Haeckel* has recorded numerous facts of variation among 

 European species of Aurelia and suggested their significance in 

 relation to problems of evolution, though in his earlier account no 

 details were given. In a later contribution^ he has, however, 

 discussed the problem in much detail, not only in connection with 

 the adults but also in relation to the embryonic development, 

 from segmentation and gastrulation on through the several transi- 

 tional stages — scyphostoma, strobila and ephyra: — up to the 

 adult, giving excellent figures and descriptions of typical examples. 



This author strongly maintains that numerical variations sus- 

 tain intimate relationships throughout the entire ontogeny, and 

 quotes Claus as holding similar views. "Ich nehme mit Claus 

 an, dass alle Zahlenabnormitaten der reifen Aurelia schon bei 

 ihrer Ephyrula-larve auftreten, und dass diese letztere sie bereits 

 von ihrer Scyphostoma-amme geerbt hat. Wenn also Scypho- 

 stoma nur 2 gegenstandige Taeniolen besitzt, so zeigt ihre Ephy- 

 rula nur 2 gegenstandige Filamenten und die reife Aurelia spater 

 nur 2 gegenstandige Gonaden." 



In connection with the recent interest in the general problems 

 of variation several brief accounts have appeared in reference to 

 this medusa, but only two have gone into any details as to facts, 

 or undertaken any analysis of them, namely, Browne^ who in 

 several contributions has discussed with pains and ability a very 

 large number of observations made upon both adult and ephyrae; 



'Das System der Medusen. Jena, 1879. 



^Metagenesis und Hypogenesis von Aurelia aurita, S. 26. Jena, 1881. 



'Quart. Journ. Mic. Soc, vol. xxxvii, pp. 245. Biometrika, vol. i, p. 90. 1901. 



