1 882.] The Siphonophores. 101 



If we were to follow precedent in our studies of the Siphono- 

 phores, we must apply to the adult the name Eudoxia instead of 

 the almost universally used Diphyes. It is just as absurd to re- 

 tain the name Diphyes to designate anything but a younger 

 stage in the growth of Eudoxia, as it would be to designate the 

 adult sea-urchin a pluteus, or to retain the word auricularia for 

 the adult starfish. The monogastric form, or the Eudoxia, is the 

 adult ; the polygastric, or Diphyes, the larva. 



There is another point to be considered. If from the embry- 

 onic feature of possessing a long axis, or stem, the relatives of 

 Diphyes are referred to the Siphonophores, is that reference a 

 good one, and would the characters as assigned to the group to 

 which Agalma belongs (Siphonophorae) hold in descriptions of 

 the adult Diphyid ? The Eudoxia has no stem-like structure, 

 which gave the name to the group, although it is a true relative. 



The comparison of Eudoxia with Agalma, or the adult stage of 

 Diphyes with the corresponding larval condition, Agalma, is evi- 

 dently legitimate, as the comparison of the developed bud of 

 Lizzia with a genus similar to the Lizzia from which it budded. 

 Although we have in Eudoxia an alternation of generation, it is 

 unlike that condition in some other animals, as in the echino- 

 derms, where the nurse cannot be homologized with the adult. In 

 some respects it resembles most closely that process of growth 

 which we are familiar with under the name of strobilation. The Eu- 

 doxia is the separated Ephyra, and the Diphyes is a free-swimming 

 scyphistoma, as far as the relation of the nurse to the adult goes. 

 Here however the parallelism ends. The same holds true also in a 

 comparison of genera of Diphyidae with the free-living proglot- 

 tis of the tape worms (Leuckart, Siphonophoren von Nizza, p. 

 29). As McCrady has already pointed out (Lectures), there is a 

 close resemblance between a Taenia and the Scyphistoma in mode 

 of strobilation, but as there is no homology between the pro- 

 glottids and the Ephyra, so there is little in common in the struc- 

 ture of the Diphyizoid and Ephyra. They resemble each other 

 simply in the mode of strobilation. 



The corresponding parts of an Agalma and an Eudoxia are 

 given in the table below : 



