106 
Z. HYDROIDA. 
Hydra, 
microscopic minuteness, but there is no foundation for any such hy- 
pothesis. * 
These are the modes in which the Hydra naturally multiplies its 
kind, but it can be increased, as already hinted, by artificial sections 
of the body, in the same manner that a perennial plant can be by 
slips and shoots. If the body is halved in any direction, each half 
in a short time grows up a perfect H ydra ; if it is cut into four or 
eight, or even minced into forty pieces, -f each continues alive, and de- 
velopes a new animal, which is itself capable of being multiplied in 
the same extraordinary manner. If the section is made lengthways, 
so as to divide the body into two or more slips ^connected merely by 
the tail, they are speedily resoldered, like some heroes of fairy tale, 
into one perfect whole ; or if the pieces are kept asunder, each will 
become a polype, and thus we may have two or several polypes with 
only one tail between them ; but if the sections be made in the contrary 
direction— from the tail towards the tentacula — you produce a mon- 
ster with two or more bodies and one head. If the tentacula, — the 
organs by which they take their prey, and on which their existence 
might seem to depend, — are cut away, they are reproduced, and the 
lopt off parts remain not long without a new body : if only two or 
three tentacula are embraced in the section, the result is the same ; 
and a single tentaculum will serve for the evolution of a complete 
creature. J When a piece is cut out of the body the wound speedily 
heals, and, as if excited by the stimulus of the knife, young polypes 
sprout from the wound more abundantly, and in preference to un- 
scarred parts ; when a polype is introduced by the tail into another’s 
body, the two unite and form one individual ; and when ahead is lopt 
* Trembley, Mem. 196—7. 
f “ J’ai ouvert sur ma main un Polype, je l’ai etendu, et j’ai coupe en tout 
sens la peau simple qu’il formoit, je l’ai reduit en petits morceaux, je l'ai en 
quelque maniere hache. Ces petits morceaux de peau, tant ceux qui avoient 
desbras, que ceux qui n’en avoient point, sont devenus des Polypes parfaits.” — 
Trembley, Mem. 248. Rome de Lisle attempted to lessen the remarkableness 
and singularity of this fact by supposing that the Hydra was a colony of minute 
animalcules held together in a moveable polypidom, represented by the thin outer 
cuticle, and of course that this cutting and division only set free a number of in- 
dependent entire beings. The hypothesis is a bold one, but has nothing in the 
way of observation to support it. See Blainv. Actinol. p. 563. 
f From the experiments of Trembley, (Mem. 235,) of a correspondent of 
Baker’s and of Baker himself, it would seem that a tentaculum cannot produce 
a new body unless a part of the head or body is removed with it (Hist. 193-4,) ■ 
but other experimentalists are said to have succeeded when this was not done. 
For the particulars stated in the text, and others equally incredible, the reader 
may consult the works of Trembley and Baker, passim . 
