TUBULARIA. 7 



The Utmost dimensions of this product are therefore as uncertain as the 

 number of regenerated hydrse whereby they are attained. Let it be al- 

 ways remembered, that the prolongation of the hydra's neck is the sole 

 medium of extension of the stem. 



The tallest of a group in confinement had reached five inches in five 

 months, after regenerating five heads ; whence it must have borne at least 

 six, including the first or original head. Instead of one, however, there 

 might have been more. With greater care, this specimen might have 

 proved more prolific. Others of the same group continued flourishing 

 during a whole year by hydrse regenerating. 



Where no articulation or node indicates the origin of a shoot through- 

 out two or three inches, either the head has never fallen, or, on reproduc- 

 tion, the neck has been incorporated so intimately with the stalk, as to 

 render the place from whence it issues imperceptible. The head has 

 never been so permanent in confinement as to show that such remarkable 

 elongation can result from the existence of a single regeneration. 



The renovated shoot is flexible, especially towards the head. Greater 

 rigidity ensues, as also of the lower portion of it, and the colour fades 

 with time. 



The reproduced hydra certainly originates below, as shall be after- 

 wards illustrated ; and sometimes the transparency of the stem exposes 

 the ascending embryo while yet at a distance from the summit. Defec- 

 tive vigour may render its ultimate evolution abortive. 



Regeneration of the head is an important process in the arrangements 

 of nature, from its being the site of not only the organs essential for nu- 

 trition of the individual, but of those instrumental in the conservation of 

 the race. 



Propagation. — Several florid clusters, resembling minute bunches of 

 grapes, with three, seven, twelve, or more berries in each, weigh down the 

 most luxuriant heads. These constitute the ovarium, composed of so 

 many capsules or cysts, each in an advanced stage, containing a single 

 embryo or foetus. The greatest disparity of size and number prevails 

 among the cysts and the clusters, nor are they of uniform figure. Cysts, 

 as mere protuberances, are associated in some bunches with those whose 



