ioo The Siphonophores. [February, 



the proboscis of Lizzia'and the stem of Diphyes, that while the 

 buds from the former separate without absorption of the stomach 

 walls, the Eudoxia appropriates a section of the Diphyes axis to 

 form essential parts of its body. 



To my mind there is no difficulty in a comparison of the Eu- 

 doxia with Lizzia 1 and with the Physophoridae. Eudoxia is the 

 adult form of which the Diphyes is the " nurse stage," so that 

 we have here a true alternation of generation as in other medusae. 

 It is natural, therefore, that the likeness between Eudoxia and 

 Agalma should be a distant one, since the latter genus never 

 passes out of the Diphyes form, or the " nurse " from which the 

 Eudoxia buds. On this account I consider the Physophoridae as 

 lower, anatomically and embryologically, than the Diphyidae. 

 Like those forms of fixed hydroids, which never drop medusa- 

 shaped buds, and never, therefore, advance out of the fixed "nurse 

 stage," the Physophoridae never attain as completely developed a 

 form as the Diphyidse. They never bud off a gonophore as the 

 medusoid bud is sometimes called, but always remain in the em- 

 bryonic form. As the Diphyes stage is comparable with a stro- 

 bila or a budding Lizzia, the Eudoxia is the completed generation 

 comparable with the adult Lizzia which drops the eggs, or the 

 sexual form. 



The following table exhibits the corresponding parts of Liz- 

 zia and Eudoxia : 



Lizzia. Eudoxia. 



Bell. Covering scale («). 



Manubrium (proboscis). Feeding polyp (polypite) (/). 



;a bud from the probos- Swimmin 

 t (aborted). 



in this article, by Professor McCrady in 185 

 rbor, p. 67). Since that date the theory has 



E. Mailer. (HaeckeL Zur Kntwick! der 



.liiller, lag. over Nogle Siphonophorer, Nat, 



