KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 59- N:0 3. 63 



sophagus. There was also a posterior, wider and shorter coeca] sac descending from 

 the lower part of the stomach, between this and the intestine. Of the liver ducts a 

 large main median one opened in front below the cardia; it was filled with nutritive 

 matter and descended to the lower part of the liver. From the uppermost liver 

 folliculi there led ducts which opened higher on both sides of the stomach, the upper- 

 most opening being situated on the left side. In the duodenum the narrower or 

 intestinal furrow appeared on the right side and the broader one on the left. Their 

 position in this specimen was thus the typical one that is found as a rule in all the 

 Chamidae, and not reversed as stated by Grieser. 



As for the anterior aorta it was observed that this descended along the left 

 side of the stomach (contrary to the statement by Grieser). On account of the 

 bad state of preservation, no details could be stated with certainty, but it seemed 

 as if a ventral trunk of the aorta was lacking and as if the gastral arteria was re- 

 placed by some small vessels branching off from the oesophageal portion of the chief 

 aorta anterior. 



As a consequence no reversation of the organization is observable in Ch. 

 pellucida compared with other species of the genus. Under these circumstances it 

 looks as if Grieser, although his investigation was performed very carefully, possibly 

 inverted his sections during reconstruction and thus confused right and left. 



7. Summary of and general remarks on the anatomy of Chamidae. 



1. The gills. 



Of the structure of the gills of Chamidae more or less exhaustive accounts are 

 given by Ridewood (1903), Anthony (1905), and Grieser (1913). The statements 

 of these authors deal, in the first place, with the fine structure of the gills, and 

 hence they more or less leave out of consideration some points of view concerning 

 on the one hand the general habitus, on the other the intimate connection of the 

 gills and the circulatory system, both matters which exhibit facts of fundamental 

 importance for an exact conception of the structure, the function and the phylo- 

 genetic development of the branchiae and, as a consequence, of their taxonomic 

 value. 



As far as their exteriör habitus is concerned the gills in all Chamidae are very 

 uniformly organized. On each side a complete ctenidium is present, emerging from 

 an axis which is strongly developed and descending vertically in the form of a 

 branchiophore. This projects freely from the side of the body on the point where 

 the nervus branchialis enters, but above this point it coalesces intimately along the 

 side of the body. Besides this nerve the branchiophore contains a strong muscle, 

 which is inserted on the shell in front of the upper end of the posterior adductor, 

 where it produces a small impression, as well as an afferent and an efferent blood 

 vessel. 



