162 ZOOPHYTES. 



But I could not discover how the yellow corpuscula, thus developing as 

 spinulse, had escaped from this specimen ; the same remark in regard to 

 the corpuscula or gemmules of the Alcyonium, may be recollected. They 

 certainly rose higher from the interior of the mass, until apparently ready 

 to burst the skin. Another important point seems very obscure, namely, 

 whether they are generated by the common mass, whether by the systems, 

 or whether they are the offspring of the individual ascidise. Here may 

 be also recollected, perhaps, a question somewhat corresponding, relative 

 to the history of the Cristatella. 



Numerous ova, or probably speaking more correctly, embryonic cap- 

 sules and spinulse at large, were secured by the different expedients adopt- 

 ed. But the latter in far greater proportion. All the former exposed the 

 embryo, inclosed as in an amnion, quiescent, the extremity of the tail so 

 completely encircling the head as to meet its own root or origin. An in- 

 ternal black speck, perhaps denoting a large vessel, was likewise visible 

 towards one side of the head. 



The spinula is of a fine yellow colour as the other is red, and some- 

 what resembles a tadpole, nor are its motions in any respect dissimilar. 



But these descriptions are only the preliminaries for illustrating a 

 metamorphosis, equally interesting, nor less remarkable than any which 

 have hitherto come under our notice. 



The evolution of the spinula from the Botryllus is slower than that 

 of the spinula; from the Ascidia papilla, and the transformation quicker. 



This wonderful change commences perhaps within a few hours of its 

 escape from its integuments. The front of the head begins to fork, and its 

 cleaving denotes the formation of incipient roots, which adhere to a solid 

 surface. 



In one instance adhesion had followed, accompanying the formation 

 uf radicles, within sixteen hours of the production of the spinula, 



Now, also, as before, the animal struggles vehemently to be free. 

 But its fixture, though commencing by only one projection, becomes rivet- 

 ted amidst the surrounding diffusing matter, or by eight radicles, securing 

 the head to the foundation, leaving the tail to vibrate above, fig. 18. By 

 gradual attenuation the tail disappears, the radicles remaining below, 

 figs. 19, 20, while a nucleus, enlarging proportionably as these diminish, is in 



