INDUCED CHARACTERS IN ASPLANCHNA AMPHORA 393 



the saccate form already mentioned. In many respects the con- 

 duct of this rotifer when bred in pedigree series suggests parallehsm 

 with Protozoa under hke handhng. But the variation, so often 

 degenerative, which Jennings has shown to result from conjugation 

 in Paramecium, finds no parallel within our experiments, so far as 

 we have carried them. On the contrary, sexual reproduction and 

 parthenogenesis seem very closely related and all but equivalent 

 processes. 



We may perhaps note in this connection that we have observed 

 a number of instances of simultaneous development of resting eggs 

 and the active young males within the body of the same parent; 

 and what is still more striking in these cases of mixed reproduction, 

 certain of the earlier developing embryos were plainly covered 

 with thin though characteristic coats resembling the resting egg. 

 In some instances such embryos were proven to become females 

 and thus undoubtedly represent fertilized eggs which because of 

 special conditions — possibly the thinner egg coats — ^were proceed- 

 ing to immediate development within the uterus quite as do the 

 ordinary parthenogenetic ova. In any (fase the close relation- 

 ship of the different types of reproduction was strongly called to 

 mind by the observation of females bearing simultaneously the 

 fully-formed resting eggs, active young males approaching the 

 birth period, and the above mentioned intermediate type of 

 reproductive body. 



As to the bearing of these conclusions, it is plain that they 

 throw much light upon our own previous experiments with this 

 rotifer, and, we think, some as well upon the extended experi- 

 ments of others upon the rotifer, Hydatina senta. Thus in our 

 own previous work, entire lines of rotifers started from resting 

 eggs chosen at random, often proved perplexingly dissimilar. 

 They possessed what we now call different potentials, some tend- 

 ing strongly toward the maintenance of the saccate type, some 

 toward the maintenance of the humped type, while others main- 

 tained this form plus the occasional production of the campanulate 

 type. It is plain now, after the experiments recorded in this 

 paper, that these contrasting lines of A. amphora may have dif- 

 fered solely because of a different parentage of the resting eggs 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 16, NO. 3 



