HYDRA. 95 



fragment continued in its place ; it became an elongated ovoid, and in 

 three weeks had generated 12 or 14 tentacula, after which farther obser- 

 vation was abandoned. 



In regard to this animal (the Hydra tuba), its propagation seems 

 more dependent on sustenance than on age and dimensions. The number 

 of organs is invariable in the higher orders, subject neither to multiplica- 

 tion nor diminution, unless to an inconsiderable extent where regenerated ; 

 but in the lower orders the discrepance is so great as generally to preclude 

 the determination of maturity by such a test. 



The aspect of the hydra is considerably diversified. In perfection it 

 is a pendent cone, or rather the gradual enlargement of a conic frustum, 

 the margin of the base environed by long silky-like tentacular organs. 



But the shape of the most vigorous is liable to some modification. 

 The disc, with the marginal tentacula, can enlarge beyond the wonted 

 diameter, and assume the resemblance of a flattened hand-bell, suspended 

 by a slender thread, while all the portion above it is diminished. — 

 Plate XIV. fig. 26 ; XX. fig. 19, a. This generally results from the sen- 

 sations of an individual, but I have seen a number at once under the same 

 appearance. 



The preceding examples in illustration of the multiplication of the 

 hydra, offer some anomalies when compared with that of other animated 

 beings. 



Amidst the functions annexed to protracted existence, scarcely any 

 except those which are essential for self-preservation are passively or ac- 

 tively incident to the earlier stages of life, and especially in such creatures 

 as shall finally acquire another and a different form. 



Perpetuation of the race seems to be reserved by Nature, in general, 

 as a property incorporated with that ultimate condition wherein all the 

 organic evolution has been attained, wherein all the animal faculties sub- 

 sist, and are exercised as indicative that the system is perfected. 



I am not aware that progeny is derived from animals in intermediate 

 stages — in those to be compared to the larva or the chrysalis, but that the 

 offspring comes of the beetle or the butterfly, as the ovum from the frog, 

 not of the tadpole. It is not said that an embryo or foetus is endowed with 



