METAMORPHOSES OF ANIMALS. ]77 



Study of their transformations. The following figures repre- 

 sent the different phases of the duck-barnacle, (Anatifa.) 



« 6 c / 



372. The Anatifa, like all Crustacea, is reproduced by 

 eggs, specimens of which, magnified ninety diameters, are 

 represented in figure 148, a. From these eggs little ani- 

 mals issue, which have not the slightest resemblance to the 

 parent. They have an elongated form, (h^) a pair of ten- 

 acles, and four legs, with which they swim freely in the 



water. 



373. Their freedom, however, is of but short duration. 

 The little animal soon attaches itself by means of its tenta- 

 cles, having previously become covered with a transparent 

 shell, through which the outlines of the body, and also a very 

 distinct eye, are easily distinguished, (Fig. 148, c.) Figure 

 148, fZ, shows the animal taken out of its shell. It is plainly 

 seen that the anterior portion has become considerably en- 

 larged. Subsequently, the shell becomes completed, and 

 the animal casts its skin, losing with it both its eyes and its 

 tentacles. On the other hand, a thick membrane lines the 

 interior of the shell, which pushes out and forms a stem, 

 (e,) by means of which the animal fixes itself to immersed 

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

 enlarges, ana the animal soon acquires a definite shape, such 



