COMPOUND ASCIDIA. 157 



eight hours, when an orifice was visible nearly about the middle ; and the 

 whole appeared as in Plate XXXIX. fig. 1, which is slightly enlarged. 



At this time the subject was disposed as a parallelogram. 



A week later it had become very irregular, as will be understood by 

 inspecting fig. 2, enlarged. 



My expectation of adhesion to the glass, and diffusion on its surface, 

 were completely realized. 



A great alteration of the upper surface had ensued on May 23. The 

 whole colony of animals had now subdivided into three portions, or distinct 

 systems ; one consisting of five individuals, the other two systems of nine 

 each, being twenty-three ascidia; in all. — Fig. 3. 



This subdivision into systems seemed very singular. Now the lowest 

 was the most regular of the three, fig. 4. The orifice above of each ascidia 

 was quite conspicuous, but I could not discover the other ; it had been too 

 low. When the central orifice is most perfect, it seems to present the 

 edffe of an elevated hollow cone. 



Systems are seated on a kind of fleshy portion, susceptible of expan- 

 sion and contraction, to which it maybe owing that sometimes the central 

 orifice or cavity is not seen distinctly. Thus, also, the different systems 

 were at times almost in contact, and at times separated by intervals. 



On June 6, the central orifice of the smallest system, fig. 3, next the 

 narrow end of the leaf, was much elevated, as were likewise that of the 

 others. 



The specimen subsequently declined. Many of the individuals had 

 disappeared in a fortnight ; and, on June 24, only ten of the whole remain- 

 ed, two being in the lowest system, which was originally the most perfect, 

 when consisting of nine animals, and four in each of the other systems. 



A partial glimpse of the internal circulation of the blood may be oc- 

 casionally obtained, when the larger, or the central orifice is much dis- 

 tended, as frequent in such products. 



This organic function is discharged in a remarkable manner, and 

 through the medium of vessels which would be deeply interesting to skil- 

 ful anatomists. To them likewise, would be due the suitable explanation 

 of the process. 



