9 



ing new cultures from il. Several times it was tried to start new cultures 

 in the way indicated by Allen and Nelson, and thus far successfully. 

 Still, I never succeeded in getting the same species of Xitzsdiia or any oilier 

 organism, which was so well lil for serving as food for the larva-, and the 

 full use of such food cultures was not obtained. In Ihe lasl working place. 

 Tobago, B. \V. I., this way of rearing the larva- was then given up, and 

 instead the larva 1 were given Fresh sea-water every day a considerably 

 more troublesome way of rearing Ihe larva-, but otherwise perfectly 

 successful. 



I may poinl out here that, while the Nil/schia-food lias proved excellent 

 For Echinoid-, Asteroid- and I lololhurioid larva-, il appears l<> be mil 

 well accepted by Ihe Ophiuroid larva*. In Ihe stomach of these larv;e is 

 very often Found the skeletons of different Silicollagellales. If cultures 

 could be raised of these forms, they would doubtless prove to be excellent 

 for rearing the Ophiurid larva-, which would be of considerable importance. 

 Possibly other Flagellates would also prove successful. 



The main object of my work being, as stated, the comparative study 

 of the larval forms it is only a matter of course thai not much altention 

 was paid to the embryological processes -cleavage, cnlerncoel formation 

 etc., as well as the process of metamorphosis or Ihe poslembryonal develop- 

 ment. Not that I think the study of these processes of minor importance; 

 on the contrary, I feel convinced that such studies carried out on dilTerenl 

 forms will give mosl important correctives to the results reached from the 

 comparatively few forms hitherto studied in these regards, such as was 

 Ihe case with the C.riuoids studied by Ihe author. But (here was simply 

 no time to do all lhal work; having lo do all Ihe work myself: collecting, 

 preserving, making biological observations, rearing cultures etc.. I had 

 simply to confine myself lo studying Ihe stages especially important for 

 my purpose; only in cases where unusual features were observed more 

 attention was paid to Ihe embryological processes, as e. g. in 1'rruiii'llu 

 Lesueuri. 



As a consequence of my having allogelher too much work lo do 1 could 

 not always get the nesessary lime for making drawings of the living larva-, 

 which was also in several cases impossible on account of I lie conditions under 

 which the cultures were reared. In such cases (lie dilTerenl stages of the 

 larvae were carefully preserved for future study at home, partly in alcohol, 

 partly mounted in Canada balsam. Now Ihis resulted in some very serious 

 drawbacks. It is, upon the whole, a very difficult Him- '" preserve such 

 larval forms as the Echinoid- and Ophiuroid larva- quite satisfactorily: 

 the arms generally shrink considerably, though not in length, of course, 

 the skeletal rods preveuting a shortening. The Iwo figures of Ihe larva of 



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