45 



the order of appearance of the marginal orf^ans I shall 

 speak of cyclic sequence . (These terms wore sugj^ested by 

 Professor f'or-ley of Johns hop-kins). New tentacles make 



their njipearance four at a time, or, so to speak, in quar- 



o 

 tettos; they are 90 apart, so that they occupy identical 



positions in the four quadrants of the marginal ring. But 



while the tentacles, and sense-organs as well, appear to 



arise in fours, the condition in the larvae and in frequent 



instances ai^iong the adults indicates that a paired origin 



is more primitive and fundamental. It is the universal 



rule in the early larvae that two tentacles appear opposite 



to one another (Fig, 11) and later the second pair of the 



quartette (Fig. 12). And it often happens that in the 



adult medusae, two members of a quartette, in opposite 



quadrants, are retarded in making their appearance. In 



Aurolia , Glaus established the theory that while the larval 



tentacles seem to come in fours after the earliest stage, 



the first four tentacles appear first two, then two more, 



as is the case in Gonionema ; (v. Glaus, 1S92), Goette 



(18S7) has examined a great number of specimens of the 



younger stages of Aurolia , and has come to the same general 



conclusion as Glaus, with regard to the primitive paired 



