137 



[wot;k from the port erin luoEoairAL station, 



NOTES on the H^MAL and WATEK-VASCULAK 

 SYSTEMS of the ASTEEOIDEA. 



By Herbert C. Chadwick. 

 With Plates XXXVI to XXXIX. 



[Read 10th March, 1893.] 



Eighteen months ago, at the suggestion of Prof. Milnes 

 Marshall of Owens College, I undertook a re-examination 

 of the structures which together form what is commonly 

 known as the blood-vascular system of the Asteroidea. 

 To those who are acquainted with the literature of the 

 Echinodermata, especially that published during the past 

 twelve or fifteen years, such a research may, at first sight 

 appear quite superfluous, the structures just named having 

 been described by Ludwig, Perrier, Hamann, Cuenot, and 

 quite recently by Durham. I was, however, fully aw^are 

 that a certain amount of scepticism existed in the minds 

 of other workers in the same field, as to the accuracy of 

 the descriptions given by one or other of these zoologists, 

 and on that account was not unwilling to examine some 

 of the doubtful points for myself. Though not yet quite 

 complete, my work is sufficiently far advanced to warrant 

 my acceptance of the invitation of the Council of the 

 Liverpool Biological Society to submit my results for the 

 consideration of its members. The close anatomical rela- 

 tion in which the so-called blood-vascular system stands 

 to the water-vascular system has led me to a study of the 

 latter scarcely less detailed than that of the former, and 

 for convenience sake I shall discuss the two systems 

 together. 



