an intermediate process of rmiltiplication; buds which are 

 developed upon the body of the hydra larva drop off and, 

 beginning as planulae, just follow exactly the same co\irse 

 of development as the parent; both parent and offspring la- 

 ter change into fully developed medusae. "Gonionema"has , 

 then, a metagenetic form of development. The mere presence 

 of a hydrula stage in the life-history is of course not 

 enough, accor-ding to generally accepted notions of the mean 

 ing of terms, to constitute alternation of generations 

 (Murbach, lcS95 , p. 496). 



These emendations of Haeckel's description of the 

 order add evidence to that already put forward (Brooks, 

 1895, p. 300) and by others that the hard and fast lines 

 drawn by Haeckel and the Hertwigs between the "Trachylinae" 

 and the "Leptolinae" , on the r^round of anatomical differ- 

 ences or of developmental features, are not borne out by 

 tho facts. The Ifertwigs (1S7S) hold that "the m-arginal 

 sense-organs (Gehflrorgane) alone furnish characteristics 

 which enable us in every case to distinguish the 'Trachome- 

 dusae' (Trachomedusae and Narcomedusae of Kaeckel) from the 

 i^ampanularian medusae (Vesiculatae) without knowledge of 

 their development". Dr. Brooks has, however, described a 

 species of Laodice which unites in its anatomical features 



