COMPOUND ASCIDIA. 171 



VII. The young ascidia is a perfect animal, wherein the vital funo 

 tions are carried on and discharged, as in the ascidise composing each sys- 

 tem of the Botryllus. 



VIII. Without the presence of other spinulce, or any sensible exter- 

 nal or internal elements, other young ascidise are generated from the first, 

 and in union with it, whereby systems are formed, and at length the Bo- 

 tryllus is a common mass. 



Plate XXXVII. Fig. 12. Botryllus verrucosus. 



13. Ascidise, a portion of the surface of fig. 12 in profile. 



14. Portion of the surface comprehending a system. 



15. Sanguiferous system in the interior of the substance 



of the Botryllus. 



16. Capsules with embryos in their integuments. 



17. Spinulse free, having quitted the integument. 



18. Spinula, with the front of the head rooted, the tail 



erect. 



19. Central nucleus, with diffusing radicles after disap- 



pearance of the tail. 



20. Central nucleus, with the radicles farther advanced. 



21. Perfect ascidia generated from a Spinula, being the 



elementary animal of the Botryllus. 



22. Duplication of the elementary animal ; a second asci- 



dia having been generated, without intervention of 

 a spinula, beside the first. 



23. The same farther advanced, by the development of a 



third ascidia. 



24. Nascent Botryllus farther advanced, as consisting of 



four ascidise. 

 All the preceding figures, except fig. 1 2, are en- 

 larged. 



Plate XXXVIII. Fig. 1. Botryllus verrucosus investing a shell. 



2. A portion of the specimen containing corpuscula. 



3. System viewed in profile. 



4. System composed of four ascidise. 



5. System consisting of five ascidise in irregular arrange- 



ment. 



