478 EDWIN S. GOODRICH. 



add fresh importance to the controversy. For^ since it has 

 become gradually established that, in the Invertebrata in 

 general, the coelom is quite distinct from the vascular system, 

 that even in the Molluscs and Arthropods the two systems of 

 cavities are of quite separate origin, it is clear that a communi- 

 cation between the two would be a very exceptional pheno- 

 menon. Now, Burger has shown by his embryological researches 

 (2) that at all events the ventral sinus, the perinephrostomial 

 sinuses, and the branches immediately deriving from them are 

 of coelomic nature and origin in Hirudo, just as they have been 

 shown to be in the Rhynchobdellid leeches ; and, moreover, it 

 has recently been contended by Oka (10) and Johansson (6) 

 that in the adult Rhynchobdellidse the vascular system remains 

 distinct and closed off from the coelomic cavities. This interpre- 

 tation is now supported by the evidence derived from the 

 structure of the interesting leech Acanthobdella, in which 

 Kowalevsky describes a closed vascular system filled with red 

 blood, distinct from the spacious coelomic cavity (7). 



All these facts are so unfavourable to the view that in the 

 Gnathobdellid leeches, alone amongst the Invertebrata, the 

 coelom is in open communication with the blood-vascular system, 

 that many authors refuse, and I think justly refuse, to admit 

 its truth without further and more definite proof. For instance, 

 Mr. Sedgwick (11), in the excellent 'Text-book of Zoology' 

 which he is now publishing, says " it is still generally held that 

 they [the vascular and the sinus systems] are continuous 

 through their finer branches. This view is, as we shall see, 

 based on insufficient evidence ; and having regard to the state- 

 ments of Oka and Biirger, it seems safe to assert as a fact that 

 the two systems are separate " (p. 517) ; and after further 

 arguments against their communication he adds (p. 519), "A 

 continuity between the vascular system and the undoubted 

 coelom of the sinuses would be a unique phenomenon in the 

 structure of the animal kingdom. '' ^ 



It was on reading these passages that I finally determined 



' Apparently adopting the view that in the Vertebrates the lymphatic 

 system is not in real continuity with the coelom. 



