CCELOM AND VASCULAR SYSTEM OF MOLLUSCA. 427 



Note on the Coelom and Vascular System of 

 MoUusca and Arthropoda. 



By 



E. Ray Laiikester, M.A., F.R.S., 



Linacre Professor, Oxford. 



The reference by Mr. Allen in his memoir published in this 

 number of the Journal to a note by me appended to Dr. 

 Gulland's paper in 1885 on '' The Coxal Gland of Limulus " 

 induces me to reprint here the report of a paper which I read 

 to Section D at the Manchester meeting of the British Asso- 

 ciation in 1887. This report was furnished by me to ' Nature/ 

 and printed in that journal in March, 1888 (p. 498). Pro- 

 fessor Julin, of Liege, also published — in a report made by 

 himtothe Belgian Academy on the proceedings at Manchester — 

 an abstract of the same paper. The report printed in ' Nature ' 

 is as follows : 



" The object of the author was to establish the fact that the 

 system of blood-containing spaces pervading the body in 

 MoUusca and in Arthropoda was not, as sometimes (and indeed 

 usually) supposed, equivalent to the coelom or perivisceral 

 space of such animals as the Chsetopoda and the Vertebrata, 

 but was in reality a distended and irregularly swollen vascular 

 system — the equivalent of the blood-vascular system of 

 Chaetopoda and Vertebrata. Hence he proposed to call the 

 body-spaces of MoUusca and Arthropoda 'hsemocoel/ in contra- 

 distinction to ' ccelom.^ It had been held by previous investi- 

 gators that in MoUusca and Arthropoda the coelom and the 

 vascular system were united into one set of spaces — whether 

 by a process of gradual fusion, or owing to the fact that the 

 two systems had never been differentiated from a common 



