312 MR. A. HANCOCK ON THE ANATOMY 



ratorj sac, by tlie aid of the branchial network, and is then 

 carried across the organ by the action of cilia ; but no definite 

 arrangement of the particles takes place until they arrive at the 

 oral or ventral lamina, where they are formed into a cord of some 

 tenacity, apparently through the agency of mucus, and are carried 

 thus moulded along this lamina to the oral orifice, and so swal- 

 lowed. This alimentary cord is conducted through the digestive 

 tube, and is rejected in the same form by the anus and excur- 

 rent tube. The cord-like faeces may frequently be seen through 

 the Avail in the lower portion of the intestine, having very much the 

 appearance of a convoluted tube lying within the canal. In some 

 of the lower forms, however, it is broken up into elongated 

 pellets. 



All this is very similar to what takes place in connexion with 

 the alimentation in the Lamellibranchs ; but in them the lateral 

 currents of particles are as well defined as the main or central 

 ones. 



Molgula and Saviguy's first and second tribes of his genus 

 Gyntliia appear to be the only forms among the simple Tunicates 

 that have hitherto been described, as possessing a well-developed 

 liver. This organ is always sufiiciently distinct in these groups, 

 and usually presents a laminated structure, but is occasionally 

 composed of tubular tufts or lobes, the colour being generally of 

 a dark olive-green. I find, however, a true hej)atic organ in all 

 the other genera examined (namely Ascidia, Stycla, Felonaia, 

 Clavelina, Sind Pero_pJiora) , quite distinct from that gland-like sub- 

 stance coating the alimentary tube in the first of these forms, 

 and which has occasionally been considered to subserve the he- 

 patic function. 



This substance is of a very peculiar character, and it is difficult 

 to say what its office really is. In all the Ascidice it forms a 

 pretty thick coating over the stomach and intestine, and is com- 

 posed of comparatively large globular vesicles, with thin reticuT 

 lated walls, each having a large, opaque, simple or compound 

 nucleus on one side. These vesicles have no communication with 

 each other, though they lie in contact and are cemented together ; 

 nor are they connected with any duct, or in any way open into 

 the alimentary tube. Blood-Channels are hollowed out, as it 

 were, amidst the vesicles ; and the reproductive organs ramify 

 throughout the agglomerated mass which overlies, for the most 

 part, the true hepatic organ. These vesicles will therefore act as 

 a sort of packing to the parts of these organs, and will give sup- 



