152 ZOOPHYTES. 



twenty-four hours of the first appearance of the Spinula. In that time it 

 has affixed, become motionless, and the tail has wasted away. But this 

 portion is also seen to continue vibrating for three days after the head has 

 been arrested. Likewise, Spinula? have continued active nine, or ten, or 

 even during sixteen days. I remember to have been surprised at finding 

 some of them no larger in nine days than at first. 



After the nucleus has formed, certain interanea are indistinctly per- 

 ceptible above and below, figs. 8, 9. The subject is not diaphanous. In 

 three months the animal is mature ; the oral and fiscal orifices have open- 

 ed ; and it has begun to colour. — Figs. 10, 11. 



Stillness is not less essential to ensure success of the regular and per- 

 fect metamorphosis, than for that of the zoophytes strictly so denominated. 

 Should the Spinulse be disturbed, the front does not affix, and the head 

 becomes strangely distorted. Yet all the alterations are rudely exhibited 

 within an enlarging integument. 



The Spinula? are produced chiefly in June and July ; also occasionally 

 at other seasons. They are generally of a red colour, sometimes fine ver- 

 milion. Many Spinula? and Ascidia? are besides very pale. 



I cannot entertain any doubt of their being living animals. 



Plate XXXVII. Fig. 1. Ascidia papilla. 



2. Another specimen. 



3. Spinula? enlarged. 



4. Spinula. 



5. Another more enlarged. 



6. Spinula affixed by the front ; the tail vertical. Cir- 



cular margin diffusing preparatory to metamorphosis. 



7. Diffusing basis, the tail having disappeared, leaving 



the front environed by radicles. 



8. Nascent Ascidia «, viewed from below ; another b, 



viewed from above. 



9. Nascent Ascidia nearly mature, the oral and faecal ori- 



fices having opened. 

 10. Young Ascidia three months old, where the interior 



is obscurely visible, viewed from above. 

 1 1 . The same seen from below. 



All the preceding figures, except the first and second, 

 are enlarged. 



