EXPERIMENTALLY INDUCED TRANSITIONS IN THE 

 MORPHOLOGICAL CHARACTERS OF ASPLANCHNA 

 AMPHORA HUDSON, TOGETHER WITH REMARKS 

 ON SEXUAL REPRODUCTION! 



CLAUDE W. MITCHELL 



THREE CHARTS 



The species of rotifer, Asplanchna amphora,- may show, accord- 

 ing to the recent observations of Dr. J. H. Powers, the following 

 types or developmental stages: first, from the fertilized or rest- 

 ing egg, there arises a small saccate female, which usually repro- 

 duces its own type through several generations; second, from these 

 early saccate females there usually arises a larger humped type, 

 which is the only form generally known to exist in nature as 

 belonging to the species A. amphora; third, there arises or may 

 arise from the saccate, or more frequently from the humped form, 

 a still larger type, which has been appropriately described as 

 campanulate. 



The question as to the number of generations normally involved 

 in these various stages and of the cause or causes for the transition 

 from one type to another are important, both for the understand- 

 ing of the species in question and for the bearing they have on the 

 general questions of polymorphism, mutation, and regulation. 



Dr. Powers suggested the definite problems of determining the 

 constancy of the saccate type, the number of generations through 



'Studies from the Zoological Laboratory, The University of Nebraska, 

 Xo. 108. 



- In thus naming this rotifier we do not wish for the present to enter into the 

 vexed question of priority or synonomy. We are simply following as closely as 

 possible English usage. We wish, however, at this point, to call attention to, and 

 credit the brief experimental work of Arno von Lange — Zur Kenntnis von 

 Asplanchna sieboldii Leydig. — which appeared in the Zool. Anz., Bd. 38, November, 

 1911. This rotifier is at least very closely allied to A. amphora. Von Lange has 

 demonstrated a saccate and a humped type, but not the third or campanulate. 



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