HIRUDINEEN STUDIEN. 



PRELIMINARY NOTICE. 



ARNOLD GRAF, PH.D., 



ASSOCIATE IN BIOLOGY, STATE OF NEW YORK PATHOLOGICAL INSTITUTE. 



THE complete paper which will be published under the 

 above title was finished in April, 1896. Many difficulties have 

 arisen with regard to its appearance in print, and when it will 

 be given to the public is as yet entirely uncertain. 



The fact that certain of the problems which I tried to solve 

 are being worked out by at least one other author compels me 

 to communicate the more important of my results in a 

 condensed preliminary form. 



The primary object of my paper was to investigate the 

 anatomy of the excretory organs of Nephelis and Clepsine. 

 During the progress of the work, however, it became evident 

 that without an insight into the finest structure of the nephrid- 

 ial cells no inferences could be drawn as to the physiology of 

 excretion. 



On the other hand, it was seen that without a fair knowledge 

 of the general organization of these animals no deeper ana- 

 tomical understanding of the organs in question could be 

 gained, and this conviction induced me to devote some time 

 to the study of the other organs. During this study it was 

 found that the lymphatic cells stand in intimate relation to 

 excretion, and considerable time was given to the investigation 

 of these cells. 



The whole paper was finally divided into: 



1. A short account of the general organization of Nephelis 

 and Clepsine. 



2. The anatomy of the excretory organs. 



3. The cytology of the excretory organs. 



4. The physiology of excretion. 



5. The origin of the pigment. 



6. The cause of the color pattern in the skin. 



