LUCERNARI.EANDTHEIRALLIES. H 



raedusoid, in fact a Charyhdean, which remains a permanent part of the body, 

 whilst the region posterior to that has become differentiated to the highest degree 

 of which the scyphostomic morph is capable. The medusoid cephalism is persistent, 

 it remains to perform, in addition to its usual functions, a part which is most com- 

 monly assigned to the hydroid; thereby illustrating, by a whole order of beings, 

 the theory that not only tlie hydroid cephalism, but the vwst Idrjldy developed 

 medusoid cepliaJism, normally, may remain a constant part of what is commonly 

 called a polypidom. 



27. Seen in this light, the Pelagia already mentioned was a free polypidom with 

 a single cephalic medusoid member, and the Lizzia, which Claparede' saw develop 

 directly from the egg, was also a free medusoid polypidom ; but probably not a single 

 cephalic member, because the same species, Ave believe, has been seen to bud 

 medusoids like itself from the sides of the maiiMhriuin. If this be true, then the 

 Lizzia in question was a free, polycephalic medusoid polypidom for a certain period, 

 in the same sense that Hydra is periodically a free, polycephalic, but dimorphous, 

 Hydromedusoid polypidom. A polypidom, so-called, may therefore consist either 

 altogether of a single variety of a morph, for instance, of all medusoids (Lizzia), or 

 of two varieties, i. e., of medusoid and hydroid, indiscriminately mixed (Hydra, 

 Coryne, etc.), or systematically disposed in their relations (Sertularia?, Tubulariae), 

 or the two varieties, the hydroid and the medusoid, may be merged into one, and 

 that one may be represented by a single cephalism, a unit, as in Lucernarife. 



28. Why a Charybdean is selectecFabove, for comparison, rather than an ATirelia 

 or Cyanea may be learned in detail in the chapter (Part XI) upon the mor- 

 phology of Charybdeidje ; suffice it to say, here, that they cannot be specially 

 homologized, neither with the strobiloid x\calephce nor with the Hydromedusa?, and 

 that they can be so compared with the Lucernarise. 



■ Claparecle, "Ucber gosclileclit. Zeug. vou Qualleu durcb Qualluu," Zeitsch. fiir Wiss. Zool. 

 18C0, vol. X, p. 401, Tuf. xsxi, ligs. 1, 2, 3. 



