102 The Origin and Transformation of Animals. 



pedicle grows narrower, and its free extremity swells out in a 

 club form. Soon an opening appears in the middle of this ex- 

 tremity, and an internal cavity is seen. Four little nipples spring 

 from the margin, and grow into arms, while others are not slow 

 to appear, and elongate in their turn. The infusory of yester- 

 day is changed into a polyp." In this state it exhibits the pro- 

 perties and ways of the polyp group, multiplying by buds and 

 by stoles* from which new polyps arise. The formation 

 thus produced resembles " horns widely expanded, but short, 

 and having their margins garnished with twenty or thirty slender 

 and moveable filaments." M. Quatrefages compares this mode 

 of growth to the proceedings of a strawberry plant, and thus 

 continues the story. " The Medusa lives some time under this 

 form, until at last, one horn acquires three or four times the 

 length of its companions, and at the same time becomes cylin- 

 , drical. A circular depression then forms near the crown of 

 tentacles, others follow at regular intervals towards the 

 pedicle, which is never reached. The body thus becomes 

 circled with ten to fourteen rings." After undergoing develop- 

 ment, these rings are successively detached, and swim away. 

 They are in fact medusoids, and gradually assume the true 

 medusa form. These remarkable steps are again compared by 

 M. Quatrefages to an imaginary case in the insect world. Sup - 

 pose, for example, " a butterfly laid an egg, that from this egg 

 there came an earthworm, which changed into a caterpillar, from 

 which other caterpillars grew like branches. Suppose, then, 

 that each caterpillar retained its head, but suffered its body to 

 be transformed into a chrysalis ; that the body was then con- 

 stricted at intervals, and that it gradually appeared to be com- 

 posed of butterflies piled one on the top of another ; that the 

 head subsequently fell off, and the butterflies flew away and 

 gradually assumed their full proportions and perfect forms." 

 This certainly would be an incredible narration, but transfer the 

 incidents from the insect world to the jelly-fish, and it is pretty 

 much what actually takes place. 



The interpretation of this class of facts renders- it necessary 

 to bear in mind the words larva, chrysalis, and perfect insect, 

 and to remember the conditions which they indicate. Turning 

 to the classes of animals undergoing the peculiar changes which 

 we have traced, M. Quatrefages proposes to adopt the nomen- 

 clature of Van Beneden, and to <c call scolex the animalcule 

 which emerges from the egg of a medusa, or any other species 

 following the same method of reproduction. Extending the 



' * " Stole (stolo, a shoot), a lax trailing branch given off at the summit of the 

 root, and taking root at intervals, whence fresh buds are developed." — Henslow, 

 Dictionary of Botanical Terms. Zoologists borrow this term to describe an 

 analogous process in certain animals. 



