106 Z. HYDROIDA. Hvlua. 



microscopic minuteness, but there is no foutulation 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 Hydra ; 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. :{: 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 a head is lopt 



* Trenibley, Mem. 196—7. 



f " J'ai ouvert sur ma main iin Polype, je I'ai etendu, et j'ai coupe en tout 

 sens la peau simple qu'il formoit, je I'ai reduit en petits morceaux, je Tai en 

 quelque maniere hache. Ces petits morceaux de peau, tant ceux qui avoient 

 desbras, que ceux qui n'en avoient point, sout devenus des Polypes parfaits." — 

 Tiembley, 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 

 aninialcides held together in a moveable polypidoni, 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. 56.3. 



I 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. 19.3-4,) ; 

 but other experimentalists are said to have succeeded when this was not done. 

 I'or the particulars stated in the text, and others equally incredible, the reader 

 may consult the works of Trembley and Baker, passim. 



