550 Mr. W. S. Macleay's Anatomical Observations 



It appears, therefore, that this singular animal completes the 

 natural circle of the genus Ascidia in the most beautiful manner. 

 It agrees with the first subgenus Cynthia in the nature of its bran- 

 chial reticulation, and of its digestive apparatus, as above said. 

 But Cynthia has two ovaries, the right one contained in the in- 

 testinal loop, and the left one coating the tunic. The first of 

 these, or the right ovary, is the only one possessed by Pandocia, 

 and the left is the only one possessed by Dendrodoa. The di- 

 stinction between the aberrant groups of Ascidia depends thus 

 upon the nature of their system of generation, as that which 

 exists between the two normal groups depends on their system 

 of respiration. 



EXPLANATION OF THE PLATES. 



Tab. XVIII. 



Fig. 1. Boltenia reniformis, seen on the right side, and of the 

 natural size. The specimen is probably contracted by 

 being in spirits, as the situation of the loop of the intes- 

 tine is indicated by a corresponding elevation of the en- 

 velope. 



P. Pedicle. 



C. Branchial orifice of envelope. 

 A. Anal orifice of envelope. 

 Fig. 2. The body of Boltenia reniformis (magnified) having about 

 one-half of the external envelope cut away, and the seve- 

 ral parts on the right side being seen in situ. Here the 

 right ovary is seen lying closely confined within the loop 

 of the intestine, of which the conical ascending rectum 

 and scolloped anus are very prominent. The oesophagus 

 is hid by the lower extremity of the right ovary, and by 



the 



