REGENERATION AFTER ARTIFICIAL DIVISION. 89 



which is essentially a single cell, do likewise. By budding, we 

 see that animals do, in a measure, arise independent of a parent ; 

 certainly independent of the egg-stage; and therefore, as all 

 individuals do not originate by maternal gestation, we cannot 

 be debarred from inquiring how many other modes of generating 

 animals there are. We have already taken note of one, namely, 

 that by budding; and of another, namely, that by self-division. 

 Let us see, now, to what extent reproduction by artificial division 

 proceeds ; under what forms, and in what or how many ways 

 and conditions it happens. 



We have seen how small a piece of the base of an Anemone 

 (p. 57) may divide off voluntarily ; now I will add that it may 

 be cut across and the base reproduce a head, and the head repro- 

 duce a base ; or it may be split lengthwise, and each half will 

 regenerate the wanting part. Infusoria were cut in several pieces 

 by Ehrenberg, and each fragment reproduced what was wanting 

 to complete its organism. 



Tremblers experiments upon Hydra. The most remarkable 

 of all these kinds of experiments are those of Trembley, upon 

 the Hydra, of which he published an account in 1744. Had 

 they not been confirmed by other observers and experimenters, 

 there is no doubt that the statements of Trembley would have 

 remained in obscurity, along with the stones of the old writers 

 about the now justly termed fabulous monsters, the Griffins, the 

 Serpents with many heads, which were called Hydras, the Tritons, 

 Centaurs, &c. Not only did this patient experimenter cut the 

 Hydras in two, but he even went so far as to slice them across 

 into numerous thin rings, and, marvellous to say, even at this 

 day, each ring reproduced a crown of tentacles at one end, and 

 elongated into a perfectly formed, naturally shaped individual. 

 With the same degree of minuteness, Trembley also split the 

 Hydras into thin longitudinal strips, which, like the rings, repro- 

 duced what was wanting to make a perfect body. Some of 

 them he split from the mouth only part-way down the body 

 and, each part reproducing what was needed, a many-headed 

 Hydra was the result; thus verifying, on a small scale, the story 



