546 Mr W. S. Mac LE ay's Anatomical Observations 



Anatomical Character. jBrcrrjc/tia/ /?omcA divided into lon- 

 gitudinal folds, surmounted by a circle of compound 

 or simple tentacula ; the meshes of the respiratory 

 apparatus destitute of papillae. Abdomen lateral*. 



SYNOPSIS OF THE SUBGENERA. 



Normal group. Ci. Cynthia Keiicutojonofthe branchial pouch 



1. Branchial pouch vi'ith more than J Ci/nthies proprea Sav. continuous. 



eight folds. Tentacula com-^ '2. Cs.sika Sav Reiicwtoionofthe branchial pouch 



pound. Liver distinct. ... l_ interrupted. 



Aberrant group. 

 2. Branchial pouch with only eight- 

 folds. Tentacula simple. Li- 



3. Styela Sav Ovaries several, one at least on 



each side of the body. 



4. Pandocia Sav Ovary unique, i. e. only the right 



one, which is comprised in the 



■^ intestinal loop. 



5. Dekdrodoa mihi .... Ovary unique, i.e. only the left 



one, which is ramose or branch- 

 ed, and situated between the 

 branchial pouch and mantle. 



The Tunicata agree with their contiguous group the Mollusca 

 in the remarkable variation that exists in their system of genera- 

 tion. Like every other solitary character that can possibly be 

 adopted for the ground-work of a zoological system, the mode 

 of generation ought to rise in importance only in inverse pro- 

 portion to its degree of variation. In a group of animals, for 

 instance, where it varies according to the species, it is evi- 

 dently of less importance, as affording natural characters, than 

 among those groups where it remains less subject to variation. 



* M. de Blainville seems not to have sufficiently studied these animals : for after 

 giving an erroneous character to the genus Ascidia, and confounding it with the genus 

 Phallusia and Clavellina, he ends with acknowledging, that with respect to the spe- 

 cies " leiir distinction est assez difficile." Art. ' Mollusque,' Did. des Sciences Natu- 

 relles. Dr. Fleming has, on the other hand, given a very good view of this natural 

 group in the art. 'Mollusca' of the Supplement to the Encyclopedia Britannica. 



When 



