104 



Dr. W. A. Herdman. 



[Dec. 8, 



I. " On the Genus Culeolus" By W. A. Herdman, D.Sc., 

 F.L.S., F.R.S.E., Demonstrator of Zoology in the Univer- 

 sity of Edinburgh. Communicated by Professor Sir 

 Wyville Thomson, F.R.S. Received November 1, 1881. 



(Abstract.) 



The genus Guleolus has been formed for a series of six new species of 

 pedunculated Simple Ascidians, belonging to the family Cynthiidae, 

 and having several anatomical peculiarities distinguishing them from 

 all hitherto described genera. The nearest ally of Guleolus is Boltenia, 

 and these two genera have been placed together as a sub-family, the 

 Boltenina-, characterised as Cynthiidae which have the body peduncu- 

 lated, the tentacles compound, and the branchial sac with more than 

 four folds on each side. 



Culeolus is distinguished from Boltenia by its remarkable branchial 

 sac (which will be described shortly), and by the external character 

 that its branchial aperture is triangular, and its atrial aperture bila- 

 biate, while in Boltenia both apertures are four- lo bed. 



One of the species, Guleolus murrayi, is described in detail — anato- 

 mical and histological — while the other five are not so fully treated, 

 but the different systems in each are compared with those of the type, 

 and the modifications are pointed out. The following are a few of 

 the more interesting peculiarities of the genus : — 



As regards the test, the disposition of the blood-vessels is the most 

 important feature. In Culeolus murrayi, throughout the greater part 

 of the test, blood-vessels are few and feebly developed. In the super- 

 ficial layer, however, the terminal twigs open into an enormously 

 developed system of globular cavities, separated by extremely thin 

 walls from the external medium, and in direct connexion with the 

 delicate hollow papillas projecting from the outer surface of the test. 

 The globular cavities and their prolongations, the papillas, contain 

 masses of blood-corpuscles, and there can be little doubt that the 

 whole system acts, to a certain extent, as an accessory organ of 

 respiration. In another species, G. wyville-ihomsoni, the vessels are 

 much more developed throughout the thickness of the test, while the 

 number of globular cavities in the superficial layer is very small. The 

 terminal twigs of the vessels, however, are prolonged beyond the 

 general surface in the form of a series of delicate and minute finger- 

 like processes, which, over some parts of the surface, are present in 

 irreat numbers. These are evidently a modification of the large papillaB of 

 G. murrayi, and both are homologous with the long hair-like processes 

 found on the outer surface of the test in most of the Molgulidas. 



The branchial sac is the most characteristic organ of the genus, and 



