of Edinburgh, Session 1880-81. 
233 
atoms are at molecular distances, and the pressure would increase 
angular velocity, and, consequently, centrifugal force at a greater 
rate than the attractive force. 
Andrew’s critical point may he explained in the same manner. 
4. On the Physical and Biological Conditions of the Channel 
between Scotland and the Faro Islands. By Sir 
Wyville Thomson. 
BUSINESS. 
The following candidates were balloted for, and declared duly 
elected Fellows of the Society: — Mr A. J. D. Cameron, the Right 
Hon. the Earl of Rosebery, Mr Walter Berry, Mr John Johnston 
Rogerson, and Surgeon-Major J. E. Tierney Aitchison, M.D. 
Monday , 20 th June 1881. 
Professor MACLAGAN, M.D., Y.P., in the Chair. 
The following Communications were read 
1. On a Class of Sturmian Functions. 
By Professor Chrystal. 
2. Preliminary Report on the Tunicata of the “ Challenger ” 
Expedition. Part IV. By W. A. Herdman, D.Sc. 
{By permission of the Lords Commissioners of the Treasury .) 
IY. Molgulidai. 
The family Molgulidai was established by Lacaze-Duthiers in 
1877,* and distinguished from the Cynthiadce , with which it had 
formerly been united by Heller, f 
Lacaze-Duthiers divides the species known to him into four 
genera, — Anurella , Molgida , Ctenicella , and Eugyra , — of which 
Anurella forms a sub-family or section the Molgulidai anuras , the other 
three constituting the Molgulidce urodelas. The character by which 
Anurella is distinguished from the other genera is the tail-less 
* Arch. Zool. Exper., vol. vi. p. 457. 
t Untersucli. ii. d. Tunic, d. Adriat. u, Mittelmeer., Abth, III, p. 1. 
