444 Glycogen in the Connective Tissue of Molluscs. [June 18, 



product " Lankester) is fluid, and dissolves to an opalescent fluid in the 

 surrounding water. 



With strong spirit, the metaplasm undergoes a very remarkable 

 and quite characteristic clotting or pseudo-crystallisation (also 

 noticed by Errera), which takes place equally well either within or 

 (in crushed specimens) outside the cell. Osmic acid yields no 

 reaction. 



It is the metaplasm or endoplastic product of the vesicle which is 

 deeply stained by iodine, and also by borax carmine, and not the 

 nucleus and cell protoplasm. I do not propose here to further 

 describe the glycogen ous vesicles, for they are described and figured, 

 both fresh and after the action of various reagents, at great length by 

 Professor Lankester and myself in the forthcoming paper to which 

 allusion has before been made, but I will take this opportunity of 

 pointing out — 



1. That these "vesicles" are the same as the "plasma cells" of 

 Brock and others, the " Langer's bladders " of very many writers, 

 and are equivalent to many of the " lacunas" of Kollmann, Griesbach, 

 &c. For many years the existence of these vesicles has been denied 

 and affirmed by two schools of observers ; we shall bring forward 

 indubitable proof in favour of Fleming and his adherents. 



2. That these cells are trustworthily figured and described by 

 Fleming ("Archiv fur Mikros. Anat., vol. xiii), and may be readily 

 seen in Anodon by the method described above, or in Helix by merely 

 spreading out a portion of the " mesentery " on a glass slip. 



5. Distribution of the Vesicles. 



These vesicles occur in Anodon wherever there is lamellar con- 

 nective tissue, except in the very muscular tip and edge of the foot, 

 labial palpi and gills, Keber's organ, organ of Bojanus, mantle edge. 



In Helix, they are found especially on the lining of the great 

 lacunar spaces, and on the " mesenteries." 



They are especially associated with the arteries in all Molluscs I 

 have examined. The brilliant whiteness of the slug's arterial system 

 is due to their presence in the connective tissue, outside the arteries. 



I have reasons for believing that these cells, or slight modifications 

 of them, are very widely distributed throughout the Invertebrata. 



6. General Remarks and Conclusion. 



Although glycogen has frequently been stated to occur iu Inverte- 

 brates (e.g., by Professor Foster for Ascaris, and by Fredericq for 

 Mya), yet I believe that hitherto it has never been definitely localised in 

 certain cells, and far from being associated with connective tissue, has 

 been thought to be for the most part a liver product. I hope to be 

 able to publish further results in the above directions at a future time. 



