LUCERNARI^ AND Til El 11 ALLIES. ^ 



and, on the other hand, as attaining to the highest independence as a controlling 

 power, when the multiple parts of a so-called compound individual separate from 

 each other, and arc singly under the influence of this power. The latter ohtains 

 when a Hydra or Actinia separates its buds from itself; or when the sexual part of 

 the annelid worm subdivides from the asexual one. Cephalism of a low degree is 

 more readily recognized in the aggregated cephaloids of Salpa than in the 

 undivided worm ; but, unlike the latter, the former remain connected cephaloids 

 (in the chain) Avhen separated from the budding stock. 



15c. By thus dividing the body of a Hydromedusa into two parts, which shall 

 contain, severally, the vegetative dominant (i. e., vegetative ccphalold) and the 

 sexual dominant (t. e., sexual ceplialoid), we avoid the absurdity of assigning 

 individuality to the egg-sac of Hydra and others of its allies which have evidently 

 a mere genital organ. Although we might be inclined to admit that some 

 ccphalisms may gradually become complete individuals, as when the buds of 

 Actinia or Hydra separate from the parent body; on the other hand, we must 

 insist that an individual cannot retain the same significance when reduced to a 

 mere genital organ, as when, in Coryne, a free medusoid (Sarsia) later in the season 

 becomes an egg-sac ; or when the free medusa of Tubularia (Ectopleura) Dumor- 

 tierii is represented in Tubularia (Thamnocnidia) spectabilis and Parypha crocea 

 by a plain sac ; or where, as in Siphonophoree, a subdivision may be either a 

 sexual medusoid, or a sexless swimming-bell, or a mere "scale." 



15d. Farther than this we need not go in order to illustrate our views in regard 

 to the relations of the so-called polymorphic individuals. Why we would rather 

 look upon them either as so many diverse forms of cephalic extremities — whether 

 hydroid or medusoid, or doubtfully one or the other, as may happen among the 

 Siphonophortc — or purely as organs under various disguises, may be found set forth, 

 in extenso, in the chapter on the individuality of Hydromedusce and upon the 

 comparative individuality of Acalephse. 



CHAPTER II. 



THE TYPE OF FORM IS NOT RADIATE. 



§ 3. The dorso-ventrally repetitive tune. 



16. Yet one word more is needed to secure to the reader a full understanding 

 of the point of view from which we are about to consider our subject. The 

 commonly received theory, that the so-called Radiata are founded upon the idea of 

 radiation, was combated by the author some five years ago,^ and the reasons for 



• Miud in Nature, ut sui)., p. 128. 



