Dallinger, Drysdale's u. Dallinger's Untersnchungen an Biflagellaten. 307 



me for many months in each year, or else arranged a. residence close 

 by for himself and family. By this means we came independently 

 upon such phenomena as presented themselves, and either was able 

 to confirm the observation of the other. 



2. Our (to us) most important determination was to observe the 

 entire series of cyclic changes in each organism in the living form 

 only; in no case under any circumstances to rely on post mortem 

 evidence, or make deductions from dried prepared" or stained speci- 

 mens. 



This resolution was formed after nearly twelve mouths of careful 

 experiment and comparison. Many of the organisms were not more 

 than the 1 4000th of an inch in length, and in every speck of 

 the ripe maceration presented themselves in such great numbers, that, 

 apart altogether from shrinkage and distoition, wholly changing the 

 relation and aspect of delicate phenomena, the aggregation was so 

 constant in drying as to make (to us) reliable results impossible. The 

 consequence was that no part of our work was done, and no one of 

 our conclusions was drawn from dead or ,,prepared" specimens. 



3. Nothing was ever admitted by us jointly, as established, which 

 had not been seen by both; first independently, and then together: 

 and this applied not only to the cyclic changes themselves, but to 

 their sequence in each of the organisms; and then drawings were 

 made which were never approved until they were satisfactory to both. 



4. To the matter of measurements we attached much importance, 

 as our experience had taught us this might almost be considered of 

 specific importance. Hence for each of the seven forms studied we 

 made alternately in the course of our studies fifty measurements each 

 (at different times). 



5. We did not allow ourselves to be satisfied with discontinuous 

 observations so far as the final results were concerned. The hiuderences 

 were of course many. At times certain morphological features pre- 

 sented themselves persistently for many days; these were possibly 

 followed by others equally persistent; but our principle was never to 

 infer a connection between even consecutive phenomena: but to ac- 

 tually observe the sequences of development from beginning to end. 

 This was only possible with some such Continuous growing stage" 

 as we devised and used; and it was this that made the work so pro- 

 longed, and made two observers indispensible. 



6. From the dates of the earlier papers it will of course be well 

 known that the observations were made with achromatic object-glasses. 

 They were however of the very highest quality, and were designated 

 the 112 th, 116 th, 125 th, 135 th and 150 th. Those who 

 have cared to follow my work for the last twenty years, will know 

 that I was amongst the earliest to point out, and endeavour to have 



20* 



