INTRODUCTION XI 



From here I went to the Zoological Institute of Vienna 

 University which was at that time headed by the famous zoo- 

 logist. Councillor Prof. Dr. Berthold Hatschek. Besides him 

 there were also on the staff Prof. Dr. Karl Camillo Schneider, 

 a well known comparative histologist of Invertebrate, Prof. 

 Dr. Heinrich Joseph, a comparative cytologist, and Dr. R. 

 Zwicklitzer who worked as assistant. I remained faithful to 

 Hydra and so I chose "The Nervous System of Hjdra" as my 

 theme for the doctoral thesis. I succeeded in using methylene 

 blue as an /;//r^-w/<^>^colouringof the complete nervous system 

 of Hjdra. In spring 1908, when I was in the eighth semester 

 of my studies, I became a Doctor of Philosophy. In 1909 the 

 results of my thesis were published in the Institute's journal 

 Jirbeiten der ^(oologischen Institute Wien und Triest. This work has 

 never been surpassed by any other study in the same field, it 

 has been quoted everywhere, and the pictures published in it 

 have often been reproduced. Because of the early appearance 

 of this work and because of the other works written by me on 

 Hydra and other hydroids (gemmation, migration of nemato- 

 cysts, etc.) that soon followed, it was not strange that after a lapse 

 of years I have been looked upon at various congresses of 

 zoologists and other meetings as being a son or even a grandson 

 of the "Old Hydra-Hadzi." 



After the completion of my studies and after I had passed 

 in 1907 the state examination, I returned to my country (Zagreb 

 in Croatia, now Yugoslavia). Here I came, after a short stay at 

 the local Zoological Museum, to the University Institute of 

 Comparative Anatomy, headed by Prof. Dr. Lazar Car. I still 

 continued to remain faithful to hydroids as w^ell as to other 

 Cnidaria and Coelenterata. It was only when I was called, at 

 the end of the First World War, to the newly founded Ljub- 

 ljana University (Slovenia, Yugoslavia) that I extended the 

 sphere of my interest to some groups of land Arthropoda (Chel- 

 icerata), particularly those which inhabit underground caves. 



For more than 40 years I have collected experience and know- 

 ledge about Cnidaria and Coelenterata, constantly thinking about 



