180 THE BILATERALITY OF POLYPI. 



utterly fail in your undertaking; and the conclusion will inevi- 

 tably be that bilaterality is the dominant feature here, to which 

 all other arrangements are subservient and secondary. But this 

 is not all that we have yet to learn from the study of the taxis 

 of this animal. Not only does the plane of bilaterality impress 

 its character upon the parts of the organization, so that they are, 

 as it were, dependents upon its two faces, but the two edges of 

 this plane have diverse significations, as clearly demonstrable as 

 that the plane which divides man's body into right and left has 

 one edge which corresponds to the back and the other to the front. 

 You may see this character even in the youngest Anemone, 

 where of the two tentacles opposite the two ends of the oblong 

 mouth one (fig. 107, A) is larger than the other; but it is most 

 especially exemplified, in the more advanced stages of growth, 

 by a peculiar fold at one corner of the mouth which is con- 

 tinued within along one edge (fig. 108, II) of the flat sac which 

 answers for a stomach. 



Certain foreign species of Anemones have this fold very 

 highly developed ; and in one in particular it projects like a great 

 trumpet, as far out as the tentacles reach.* Which of the two it 

 is, the back or the front, that this fold corresponds to, naturalists 

 are not agreed upon ; but as the discoverers of the Anemone 

 with the trumpet-like fold state that its food is passed into the 

 month down this funnel, we may infer from analogy that the 

 side of the body in which it lies is the predominant one, and 

 therefore is entitled to the designation of the front, or ventral 

 side. But still the determination is not an absolute one, nor is 

 it necessary for our purpose that it should be so ; suffice it to say 

 that we can recognize two antagonistic sides above and below 

 a horizontal plane which divides the body into an upper, or dor- 

 sal, and a lower, or ventral region. 



Thus in those Zoophytes which, from the comparative sim- 

 plicity of their organization, and the manifold lateral repetition 

 of parts, must be looked upon as the lowest of the grand divis- 



* Sipkonactinia Bceckii. Danielssen and Koren. Fauna Littoralis Norvegiae, 

 2 de liv. 1856, p. 88, PI. xn. figs. 4, 5, 6. 



