PROTOSTirniA'PA OF MOLGULA MANHA'I'TENSIS. 157 



The point which vequires i-ectificatirm relates to the epi- 

 eai'dium. With regard to this important structure I wrote 

 as follows : ' — " I have seen the epicardiuni in Clavelina, which 

 was described by van Beneden and Julin, but no trace of such 

 an organ in Ciona, although it was held as probable by these 

 authors that it occurred in all Tunicates." A few months 

 later, in vol. 35 of this Journal, appeared a paper by Mr. 

 Newstead describing the communication of the capacious 

 perivisceral cavity of Ciona with the cavity of the branchial 

 sac by means of a pair of retro-pharyngeal orifices. ~ 

 More recently M. Damas^ has shown (1) that the perivisceral 

 cavity of Ciona is paired, and (2) that it is the homologue 

 of the epicardiuni of Clavelina. Finally, Professor Julin 

 (op. cit.) has described the development of this structure from 

 the beginning to the end. 



When it is known that the epicardiuni (or rather the homo- 

 logue of the epicardium) is larger in Ciona than in any other 

 Ascidian, it may seem unaccountable that I should not have 

 seen it. As a matter of fact, however, Damas finds nothing 

 surprising therein, since, according to his observations, the 

 epicardial diverticula occur at a later stage than those 

 examined by me. 



Damas and Julin have shown that the epicardial diverticula 

 in Ciona are the direct extensions of the fundus of the 

 pharynx on either side of a ridge called the retro-pharyn- 

 geal crest, which is in continuity with the right lip of the 

 endostyle (Julin). Throughout the nepionic period the epi- 

 cardial diverticula are little more than the somewhat deepened 

 pharyngeal fundus ; in fact, the latter is shown by Julin to be 

 the primordium of the epicardiuni. 



In Clavelina, as shown partly by Seeliger (1885), and 



' Tills Journal, vol. 34, pp. 351, 352. 



2 A. H. L. Newstead, "On the Perivisceral Cavity of Ciona," 'Quart. 

 Jonrn. Micr. Sci.,' vol. 35, July, 1 893, pp. 119—128, PI. 8. The author confirms 

 van Beneden's and Julin's suspicion that the perivisceral cavily of Ciona 

 represents the epicardiac tubes of Clavelina. 



^ D. Damas, " Les formations epicardiques chez (Hona inteslina is," 

 'Archives de Biol.,' vol. xvi, 1S99, pp. 1—25, pi. 1 — 3. 



