COMPOUND ASOIDIA. 165 



nectine channels visible. While an additional ascidia is thus generated 

 in these early stages of the Botryllus, it appears that the duplication or tri- 

 plication of the radicles is also concomitant. — Fig. 24. 



Quiescence is a condition alike essential to the metamorphosis of the 

 spinula here, as we have seen of the Ascidia papilla, and of the zoophytes. 

 The front of the head dilates on its application to the solid surface, where 

 the change is to ensue. Radicles rivet this, which is to be the under sur- 

 face of the nascent ascidia, to its site, while the vertical tail, vibrating 

 above, wastes away. A diffusing matter around contributes to secure the 

 whole. But disturbance of the spinula prevents adhesion ; the head is 

 distorted, aud the radicles, dispersed within the transparent growing inte- 

 gument, project in front, as the animal lies in a horizontal position. Some 

 disorderly influence has impaired their regularity. 



The orifices of the nascent ascidia are very short tubular projections, 

 with a circular even edge, as I have ascertained by protracted observation. 

 It is not of simple, soft bodied animals, ready every hour to assume a dif- 

 ferent appearance, that the true form can be at once discovered. In a 

 week from its embryonic state, confined within the amnion, the young 

 animal is matured, and it feeds. Buoyant particles dispersed among the 

 water disappear quickly by attraction and absorption of the oral orifice, 

 and sometime afterwards a small excretory heap is found under each. 



Several of the young Botrylli thus bred in my possession, survived 

 about eight months, though I could not find that any of them consisted of 

 above five individuals. The diameter of the base or under surface of the 

 group in this stage did not exceed five lines. Meanwhile the whole ac- 

 quired an olive-green colour. 



The yellow internal corpuscula, whence the spinulse are produced, 

 have appeared in June and in October. Thence the Botryllus breeds in 

 summer. 



The large specimen cut as a piece of solid jelly under the knife ; then 

 the systems proved almost superficial, and below them was displayed the 

 organization of the sanguiferous vessels. 



In eight days from the first this specimen was in decay, tinging the 

 water green. 



