INDUCED CHARACTERS IN ASPLANCHNA AMPHORA 395 



Lastly, we find in our results suggestions toward the explana- 

 tion of many of the puzzling diversities of condition in which 

 Asplanchna amphora and allied rotifers have been found in 

 nature. We will not enter into details. But it is worth pointing 

 out that some of the systematic students of the genus seem to 

 have known only the saccate type ; a number have now found, in 

 at least feeble development, the rotifer in its dimorphic condition, 

 that is, the saccate type giving rise to the humped form; while it 

 seems doubtful at the present time whether the trimorphic condi- 

 tion, which is so copiously present in our vicinity, has as yet been 

 met with elsewhere. After making full allowance for the differ- 

 ent methods of study, and so forth, it seems highly probable 

 that this rotifer and its immediate allies exist in nature in different 

 degrees of development in different localities. Under the least 

 favorable conditions it is possible that the saccate type only has 

 been produced. Under more favorable conditions the potential 

 has been raised and inheritable germinal variations have been 

 induced, making possible the regular production of the humped 

 type. Much more rarely, under conditions favoring the develop- 

 ment of the species in unusual numbers, the striking though less 

 fixed type which we call the campanulate has resulted. This 

 type transmits its form, never to all, but always to a part of its 

 offspring. 



In the brief period of our experiments — about eight months — we 

 were unable to produce types which were stable save when bred 

 under approximately uniform conditions. Extreme starvation or 

 sudden change in opulent nutrition would bring about a reversion 

 to a simpler or stimulate to a higher type. In so far, our work 

 falls short of offering conclusive evidence that the processes which 

 we have described are related to species formation. Nevertheless 

 it is easy to imagine that similar steps may now and then become 

 more permanent in nature. In any case, it is interesting to know 

 that the marked morphological changes induced by nutrition are 

 not confined within the bounds of parthenogenetic series only, 

 but, as far as our experiments show, are equally transmitted by 

 the sexual process. This it seems to us, renders it at least not 

 improbable that the mutational changes shown by this rotifer are 

 phases of a true species-making process. 



