No. I.] THE SENSORY CLUBS. 3OI 



the plane of the ex-umbrella. These features of resemblance 

 to the Trachylinae are still more marked in many of the Euco- 

 pidae with solid tentacles. 



The Systematic Rank of Laodice. 



I have in this paper put such terms as " Vesiculatae," " Lep- 

 tomedusae" and " Leptolinae " in' quotation marks, while I 

 have used the term Trachylinae without them. 



This use of words is not capricious, although it may seem so. 

 The "Vesiculatae" of Hertwig are the " Leptomedusae " of 

 Haeckel, who has proposed to divide them into " Vesiculatae " 

 and "Ocellatae"; while the "Ocellatae" of Hertwig are the 

 " Anthomedusae " of Haeckel, which, together with his " Lep- 

 tomedusae," form the sub-legion " Leptolinae." This, together 

 with the Trachylinae, form the " Craspedota." 



Every one of these terms is based on natural affinity, but no 

 group which divorces hydroids without free medusae from their 

 allies with free medusae is natural, nor should it be admitted 

 into the system of zoology. The orders Sertidariae (Agassiz), 

 Tubidariae (Agassiz), and Trachylinae (Haeckel) are natural; 

 but while it is often convenient to talk of hydroid medusae, as 

 distinguished from hydroids, they should not be designated by 

 technical terms, and I shall speak of veiled medusae, of cam- 

 paniilarian medusae, and of tubularian medusae, rather than 

 "Craspedota," " Leptomedusae," and "Anthomedusae." 



Are the Trachylinae derived from one of the other groups of 

 Hydroidea, or do the various groups converge in such a way as 

 to indicate common descent from some remote and unknown 

 ancestor.? It is usually held that the Trachylinae are the 

 descendants of medusae which arose on hydroid cormi, but if 

 the common meeting-point is more primitive than any existing 

 form, there can be no direct proof of this view. Laodice 

 and the other campanularian medusae with ocelli are true 

 campanularians; and A. Agassiz has shown that the blastostyle 

 and medusae-buds of Laodice (Lafoea) calcarata are inclosed in 

 true chitinous gonangia. 



There is also a general agreement among specialists that 



