DEVELOPMENT OF TTJBULARIA COKONATA. 



87 



and is effected by mere growth from the original polyp at certain de- 

 terminate points of its substance, which points are similarly situated 

 with respect to each other in all the individuals belonging to the same 

 species. At these points appear gemmee exactly similar, both in texture 

 and mode of growth, to the body from which they spring ; and the buds 

 thus produced give birth to others in a precisely similar manner. 



(198.) In like manner when a stem is cut off transversely, a bud is 

 developed from the cut extremity, which by its growth prolongs the 

 original trunk. When this kind of gemma has attained to a sufficient 

 size, there arises from its extremity a little crown of tubercles ; sub- 

 sequently a second becomes manifest, at some distance from the first ; 

 and as the growth of these tubercles continues, each of them becomes at 

 length developed into a tentacle. The tentacle, therefore, grows from 

 the body exactly in the same way as the bud from the stem, the only 

 difference being that the former is solid, and the latter tubular. 



(199.) The growth of the horny sheath of the polypary (fig. 42,6) 



Tubularia coronata. b, the polypary, or horny sheath ; c, living substance of the animal ; 

 d, boundary between the individual and the common stock ; g, tentacular arms ; &, tentacular 

 zone ; h, mouth ; n, reproduction by continuous gemmation ; o, ovigerous capsules. (After Van 



exactly keeps pace with the development of the soft substance, and even 

 advances beyond it. 



