158 ARTHUR WILf/EY. 



finally by van Beneden and Jnlin (1887), the pericardium and 

 epicardium are develo]ied from a connnon primordium. 

 DaniHs, wlio saw the origin of tlie epicardial diverticula in 

 Ciena, found tliem in complete independence of the peri- 

 cardium. 



Thus Damas describes the orig-in of the epicardium apart 

 from the pericardium, while I referred to the latter in igno- 

 rance of the former. 



It seems quite clear that the epicardium of Ascidians is a 

 very important morphological entity, and, iii fact, this has 

 already been recognised in a practical manner by M. Giard, 

 who has instituted an interesting comparison between the 

 Tunicate epicardium and the post -branchial bodies of Verte- 

 l)rates.' 



Note. — As a matter of fact my origin al account of the 

 double nature of the pericardial primordium in Ciona, and of 

 the origin of the heart by splitting of the j^ericardial septum, 

 has been fully confirmed quite recently by Dr. Marc de Selys 

 Longchamps {" Developpement du coeur, du pericarde, et des 

 epicardes chez Ciona intestinalis," 'Bull. Ac. Belgique,' 

 No. 6, June, 1900). In another article in the same bulletin, 

 by Selys Longchamps and Damas (" Recherches svir le 

 developpement post-embryonnaire et 1' organisation de Mol- 

 gula ampulloides, P. J. Van Beneden"), the following 

 passage occurs : — " Ce stade a six protostigmates que nous 

 avons observe chez I'ampulloide rappelle un moment corre- 

 spondant du developpement des autres Ascidies simples. 

 Son origine n'ayant pas encore ete mise completement hors de 

 doute, nous ferons remarqner la complete ressemblance de 

 la presente description avec celle fournie par A. Willey (1) 

 chez la Molgule des iles Manhattes." 



' Alfred Giard, "Sur I'lioniologie des tliyro'ides latorales (corps jiost- 

 braucliiaux, Verdun) avee I'epicarde des Tuuiciers," ' Coniptes reiidus Soc. 

 Biol.,' April, 1898. 



