GGELOM AND VASCULAR SYSTEM IN THE LEECH. 479 



to try and solve the question ; and although^ at first, I was 

 strongly in favour of the view held by Sedgwick, the unmis- 

 takable evidence of the facts has forced me finally to adopt the 

 older interpretation. The result of these researches is to prove 

 without doubt that the continuity exists.^ 



It was Leydig who first showed that in the leeches there are 

 two systems of vessels, a contractile and a non-contractile. De 

 Quatrefages and Leuckart compared the former with the 

 vascular syst<^m, the latter with the body-cavity of the 

 Chsetopods. In a classical paper on the structure of leeches, 

 Professor A. G. Bourne carefully traced out the relations of 

 the main cavities of the two systems throughout the Hiru- 

 dinea (1). He concluded that in all leeches a continuity exists 

 between the two sets of cavities. Further, that in the 

 Rhynchobdellidae there are four main longitudinal blood- 

 vessels, lying in four longitudinal sinuses of coelomic nature;^ 

 the nephrostomes lie in coelomic spaces, more or less cut off 

 from the ventral sinus containing the nerve-cord. In the 

 Gnathobdellidse, Bourne believed that '^ (1) all trace of lateral 

 sinus and of the dilatations connected with it has vanished ; 



(2) all trace of the dorsal and ventral vessel has vanished ; 



(3) the lateral vessels with their connections and the dorsal and 

 ventral sinus system are placed in communication only through 

 a new development, viz. botryoidal tissue.^' 



The blood system of the leeches has been studied by a large 

 number of investigators ever since the time of Cuvier. We 

 need not give a detailed historical review of the work of the 

 early authors, of which an excellent account has already been 

 given by Moquin Tandon (9) and Gratiolet (4) ; it is sufficient 

 to point out that in 1862 Gratiolet (4) gave an admirable de- 

 scription of the vascular system of Hirudo, to which little has 



^ The fluid coutaiued iu the channels is, therefore, a hsemolymph in the 

 true sense of the word, and the combined contractile and non-contractile 

 systems may justly be called the hasmolymph system. 



^ The distinction of these spaces by the terms "vessel" and "sinus" is 

 not a very convenient one, but it is difficult to find a better. The word 

 channel may be used as an indifferent term. There are some channels, the 

 vascular or ccelomic nature of which cannot at present be determined. 



