324 REPARATIVE POWERS OP LOWER ANIMALS. 



Of certain kinds of Holothuria (fig. 67), which eject the entire 

 mass of viscera under the influence of alarm, it has been ob- 

 served that they not only continue to move about as if nothing 

 had happened, but that, under favourable circumstances, they 

 regenerate the whole of the digestive and reproductive appa- 

 ratus thus parted-with. Next to Zoophytes, there are no 

 animals in which the regenerative power is known to manifest 

 itself so strongly as the lower members of the Articulated 

 series, such as the inferior Entozoa and the Turbellaria (Zoo- 

 LOGY, 924), among which last we find the Planaria almost 

 rivalling the Hydra, although it is an animal of much more 

 complex structure. The common Earthworm can reproduce 

 either the head or any portion of the body of which it may 

 have been deprived; but it cannot be multiplied by the division 

 of its body into two or more parts (as asserted by some), since 

 these parts, although they continue to move for a time, soon 

 perish. There are Worms allied to it, however, in which the 

 regenerative power is sufficient to produce the whole body 

 from a separated fragment; and no fewer than twenty-six 

 have thus been made to originate by the subdivision of a 

 single individual. In the higher Articulata, such as Crus- 

 tacea, Insects, and Spiders, the reparative capacity is limited 

 to the restoration of limbs ; and even this would seem to be 

 seldom preserved in perfect Insects, being restricted to the 

 larval period of their lives. Little is known of the regene- 

 rative power possessed by the higher Mollusks ; but it has 

 been affirmed that the head of the Snail may be reproduced 

 after being cut-off, provided the cephalic ganglion be not 

 injured, and an adequate amount of heat be supplied. 



390. It is only among the cold-blooded members of the 

 Yertebrated series, that the reparative power extends to the 

 renewal of entire organs ; and this seems limited in Fishes to 

 the reproduction of portions of the fins which have been lost 

 by disease or accident. In JBatrachia, however, it has been 

 found that entire new legs, with perfect bones, nerves, 

 muscles, &c., may be reproduced after severe loss or injury 

 of the original members ; and even a perfect eye has been 

 formed in place of one that had been removed. It is inte- 

 resting to observe that the exercise of this reparative power 

 essentially depends upon the temperature in which the animal 

 is living; the reproduction of entire members apparently 



