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one's self in, that of attempting to take a little of the cream from 

 other peoples' researches. Some slight excuse may perchance be found 

 in the circumstances that several years of my life have been devoted 

 to the solving of this puzzle of the mode in which animal development 

 is accomplished, and that the alternation solution has been persistently 

 stuck to, in spite of the fact that it was almost universally ignored, 

 or, where noticed, looked upon as absurd. 



My own researches have been sufficiently laborious and costly in 

 time and money, without the additional burden of new investigations 

 into, for instance, the conjugation of the Infusoria. With such works 

 as those of R. Hertwig, and still more, of Maupas to fall back upon, 

 one is relieved from anything but the utmost acknowledgment of what 

 is due to them. If these researches had oliered serious obstacles to 

 the further elucidation of the problem, two courses would have been 

 open. The views might have been dropped as probably erroneously 

 based, or new researches might have been attempted. In many ways 

 I consider myself as fortunate in having had the track cleared, and 

 all the serious work done, by such distinguished observers. 



Maupas' diagram of the conjugation ofVorticella, reproduced 

 in Fig. 5, yields at a glance abundant evidence demonstrating the 

 intricate nature of the process. Complicated as are the phenomena 

 which ensue on conjugation , their explanation, as processes solely 

 concerned in the formation and differentiation of new individuals, 

 furnished with macro- and micronuclei, will hardly be challenged. 



The two divisions B and C of the micronucleus of the "macro- 

 gamete" are also simply explicable, for they differ in no respects from 

 corresponding ones leading to spore-formation and reduction in other 

 forms. Of the four spores (c) produced three are abortive, whilst the 

 fourth, representing the sporozooid, divides (D) as in other cases, 

 once. Owing to the circumstance that the other individual, the micro- 

 zooid, has become reduced in size, and has lost all power of recep- 

 tivity for a conjugating gamete, the one {d'^), which in the ancestry 

 performed the functions of a "wandering nucleus" passing over to 

 what is now the micro-zooid, no longer possesses functions and under- 

 goes atrophy. It is still formed, because its formation is a necessary 

 incident in the origin of the functional one. This abortive gamete {d^) 

 corresponds, if anything in the conjugation of the Infusoria does so, 

 to one of the polar bodies formed in oogenesis, i. e. as a rudimen- 

 tary gamete. It will be noted that it also has its abortive equivalent 

 in the micro-zooid (rf^). 



Regarding the phenomena in the latter prior to actual conju- 



