280 PROF. W. A. HERDMAN OX THE 



folds on each side o£ the branchial sac. In my " Revised Classification of 

 the Tunicata/' read before this Society in February 1891 *, I therefore placed 

 the species in a separate genus, Forhesella ; and in 1893 t I redescribed and 

 figured it in more detail. In 1892 Lacaze-Duthiers and Delageij:, from the 

 examination of specimens found off the coast of Brittany, quite independently 

 came to the same conclusions as my own, and had proposed to form for the 

 reception of this species a new genus ^'"Forhesia" ; but on receiving my paper 

 of 1891 they accepted the generic name Forhesella there-in defined. 



More recently liartmeyer, in the new edition of Bronn's " Tier-Reichs," 

 1909, p. 1335j places both Forhesella and Forhesia as synonyms of his genus 

 Pyura, the modern equivalent of Cynthia. His defence for so doing is 

 that what seem the two most notable characteristics of Forhesella tessellata^ 

 namely, the tessellated or plate-like condition of the test and the small 

 number of folds in the branchial sac, are both characters that are fomid in 

 other species which he brings under his comprehensive genus Pyura. It 

 may be remarked, however, that even on his own showing the combination 

 of these two characters is not found in any other species ; but, apart from 

 that, it is quite questionable whether species showing such a small number of 

 folds in the branchial sac ought to be placed in Pyura (= Cynthia). In his 

 discussion of the matter Hartmeyer states that two or possibly three species 

 show five folds on each side, and that one {Pyura stuhenrauchi, Meichaelsen) 

 has on each side only four folds. The species that have five folds on each side 

 I would regard as undoubtedly members of the genus Pyura or Cynthia, but 

 the species with only four folds, if the existence of that character as a normal 

 condition is established, I would unite with the species tessellata in the genus 

 Forhesella. The species Cynthia stuhenrauchi of Michaelseu § was described 

 from a single preserved specimen brought home from the Straits of Magellan. 

 In such a case it is of course quite possible that the single specimen examined 

 was an abnormal individual, and I doubt whether on such evidence we are 

 justified in making the proposed change in our classification. 



I make a considerable distinction between the presence of eight folds and 

 of ten. Four folds on each side is a well-marked character of the subfamily 

 Styelinse (according to some authors the family Styelidse), while the Cynthias 

 have a variable number of folds, from five on each side upwards. In dis- 

 cussing such matters of classification one must look at the problem from the 

 standpoint of phylogeny. The ancestral Styelinse and Cynthiinse diverged 

 presumably when their common ancestors had four folds on each side of the 

 branchial sac, and thereafter the Styelas seem to have fixed the character of 



* Journ. Linn. Soc, Zool. vol. xxiii. p. 558. 



t Journ. Linn. See, Zool. toI. xxiv. p. 451. 



X Mem. Acad. Sci. Inst. France, t. xlv. No. 1, p. 137. 



§ Zoologica, Bd. xxxi. p. 102 : Stuttgart, 1900. 



