146 



METAMORPHOSES OF ANIMALS. 



marine bodies, after the loss of its tentacles. This stem 

 gradually enlarges, and the animal soon acquires a definite 

 shape, such as it is represented in figure 148, f, attached to 

 a piece of floating wood. 



374. There is, consequently, not only a change of organi- 

 zation in the course of the metamorphoses, but also a change 

 of faculties and mode of life. The animal, at first free, 

 becomes fixed ; and its adhesion is effected by totally 

 different organs at different periods of life, first by means of 

 tentacles, which were temporary organs, and afterwards 

 by means of a fleshy stem designed especially for that 

 purpose. 



375. The Radiata also furnish us with examples of vari- 

 ous metamorphoses, especially among the star-fishes. A 

 small species living on the coast of New England (Echi- 

 naster sanguinolentus) undergoes the following phases 

 (Fig. 149). 



Fig. 149. 



376. If the eggs are examined by the microscope, each 

 one is found to contain a small, pear-shaped body, which 

 is the embryo (e), surrounded by a transparent envelop. 

 On escaping from the egg, the little animal has an ob- 

 long form with a constriction at the base. This con- 

 striction becoming deeper and deeper forms a pedicle, 

 (p), which soon divides into three lobes. The disc also 

 assumes a pentagonal form, and five double series of vesi- 

 cles, which are the first rudiments of the rays, are seen 

 to form in the interior of the pentagon. At the same time, 

 the peduncle contracts still more, and at last is entirely 

 absorbed into the cavity of the body, and the animal soon 

 acquires its final form (m). 



