ON THE EXISTENCE OF COMMUNICATIONS 



BETWEEN THE BODY-CAVITY AND THE 



VASCULAR SYSTEM 



St 



ARTHUR E. SHIPLEY, M.A. 



Fellow of Christ's College, Cambridge. 



In the General Considerations which follow Mr Sedgwick's 

 recent paper upon the development of Peripatus Capensis, he sums 

 up the characteristics of the coelom in the following terms : (i) the 

 coelom does not communicate with the vascular system ; (ii) it 

 communicates with the exterior through nephridial pores ; (iii) its 

 lining gives rise to the generative products; (iv) it developes either 

 as one or more diverticula from tlie primitive enteron, or as a 

 space or spaces in the unsegmented or segmented mesoblastic 

 bands (in the latter case called mesoblastic somites). Later on 

 he calls attention to the fact that " there are certain animals to 

 which the above general considerations as to the distinctness of 

 the coelom and the vascular system do not apply." The animals 

 here referred to are the Hirudinea and the Nemertea. In a later 

 paper Sedgwick suggests the possibility that the nephridial 

 funnels of Leeches might possibly open into a closed vesicle which 

 lies in, but does not open into the vascular system. That some 

 such structure may have been overlooked is rendered more 

 probable when one recalls the number of able observers who failed 

 to observe similar structures in Peripatus, and the fact that so 

 careful a worker as Oscar Schultze overlooked the comparatively 

 large nephridial funnels, when working at the excretory system of 

 Clepsine. 



Last term I devoted some time to the examination of these 

 points. The forms I investigated were Clepsine, and to some 



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