590 MÀYNARD M. METCALP, 



At first they are branched, forming a network, but as the flattening 

 proceeds, the interspaces of the network become smaller, until they 

 are mostly obliterated. In older individuals the nuclei of the cells 

 cannot be found, nor are there any swellings upon the membranes 

 to mark the points where they formerly lay. 



The periganglionic membrane is always more or less interrupted. 

 The membrane between the optic chamber and the periganglionic 

 blood sinus is a continuous sheet, except at the point where the 

 large perforation allows the blood in the two spaces to mingle. 



The Biological Laboratory 

 of the Woman's College of Baltimore, Sept. 20, 1899. 



In the earlier pages of this paper frequent reference is made to 

 the Ascidian Herdmania hostrichohranchus. This is a misnomor. For 

 Herdmania hostrichohranchus read everywhere Hostrichohranchus molgu- 

 loides. (For explanation of this error see the footnote 2) on page 583 

 and 584.) 



