4(>2 



THE AMERICAN NATURALIST [Vol. XL VI 



consisted chiefly of Brachionus and Hydatina. These 

 organisms were not numerous, however, and were ex- 

 hausted just as the countless hordes of the young Moinas 

 appeared. Under these circumstances a wholesale tran- 

 sition to Moma-feeding occurred, even while the As- 

 planchna was in its earlier phases of development. The 

 smaller humped forms had just begun to appear when 

 the Moina-feeding began, both by these humped individ- 

 uals and by not a few of the larger saccates. The species 

 became for a few days indescribably chaotic. So far as 

 body form was concerned, transition stages could be 

 found between every possible type and variation. This 

 is the only instance in which I have found the saccate 

 form giving rise to the campanulate without the humped 

 intermediate, but it certainly did so to a considerable 

 extent in this case. The outcome of Moina-feeding in 

 this pond was the establishment, after about nine days, 

 of a new equilibrium for the species. The giant campan- 

 ulates had become in this instance, and this instance only, 

 among my observations in nature, the preponderant type, 

 reproducing their own form in the main, but also a few 

 slender, long-humped individuals. Of these latter a very 

 few managed to ingest the Moinas and to reproduce, while 

 the majority showed empty, shrunken stomachs and no 

 developing embryos. All traces of saccate and transi- 

 tional forms had disappeared. 



I will note, in passing, that the campanulate form which 

 is produced by the Moina-feeding is not quite identical 

 with that procured by cannibalism. The size reached is 

 even a little larger, and the animals have the appearance 

 of being even more powerful in general musculature; 

 but the flaring corona never becomes quite so extreme; 

 the animals never assume quite the bell-like form which 

 the most majestic cannibals present. 



(To be concluded) 



