TRANSFORMATIONS. 309 



lowed it to the development of the Ascidia form. By 

 means of the rapid vibrations of the powerful tail, the 

 little tadpole swims for short distances through the 

 water, with more effort than effect. After a while, it 

 rests ; swims again, and again rests ; till at last it moves 

 no more. A coloured eye- speck is visible on the sur- 

 face, destined to be absorbed ; the tail is beginning to 

 disappear (in some cases it is separated by a spontaneous 

 constriction at its junction with the body, in others it 

 appears to be gradually absorbed) ; one or more warts 

 are seen budding from the opposite extremity of the 

 body. These last secrete a cement by which the animal 

 is finally attached to its support, shell, stone, or sea- 

 weed, either growing out into creeping and adherent 

 root-threads, or enlarging into a broad base, from which 

 the body begins to grow upward. After a while the 

 two orifices are formed ; first within, on the mantle, 

 before the exterior test is pierced ; then the internal 

 organs, the gill- sac, and the pulsating heart, if it be 

 one of the transparent species, become recognisable ; 

 the single eye-speck, a temporary organ, pales and dis- 

 appears ; and the permanent circles of visual organs 

 are formed around the siphonal orifices. And thus the 

 Ascidian is developed. 



The genera Ascidia and Cynthia consist of isolated 

 distinct individuals ; the Clavelina and the Perophora 



