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larvie, which, upon careful study, seemed to be larval forms of some trematode. 

 These larv;t? had been observed before and designated as tetracotyle from their 

 four sucker-like depressions. The complete literature on. the form in question 

 showed that its anatomy was practically entirely undetermined, and study re- 

 vealed that the few statements made by the earlier observers were not correct. 

 The form was therefore subjected to a critical morphological study and its anatomy 

 fairly well determined. The observations weie, however, extended further. It 

 was necessary to determine of what species this was of the larval stage. Follow- 

 ing the experiments of the Italian Helminthologist, Ercolani, some of these larvce 

 were fed to a duck in the hope that the adult forms might make this bird a tem- 

 porary or forced host at least long enough to mature. The excreta were ex- 

 amined prior to the feeding to see whether the duck might already be harboring 

 similar parasites. None such were found. After about ten days, typical trema- 

 tode eggs appeared in the excreta, and upon examination the intestines of the 

 duck yielded about forty mature holostomida?. This seemed a clear case of es- 

 tablished identity. These forms had been noted but once before by Ercolani, and 

 he had limited his oliservations to a few external points. These mature forms 

 were then sul)jected to a similar morphological study, and because of the excel- 

 lent material aflbrded, their anatomy and histology was determined with more 

 success than is usual in dealing with such forms. Ercolani had wrongfully clas- 

 sified the form, and comparison with all the determined species showed this form 

 to Ije a new one to science. 



It was now hoped that the eggs found in the excreta might be watched in 

 their development until they should as larv:e enter again the body of a snail and 

 so complete the life-cycle of this trematode. The early segmentation was followed 

 and its development toward a ciliated embyro noted, but it was not possible to fol- 

 low the cycle farther. There is, however, from what we know of related forms, 

 no special difficulty in bridging over this gap. 



The results of the observations briefly summarized are these: 



(1.) The determination of the anatomy of the tetracotyle larvse. 



(2.) The identity of this larv;v with a definite adult form of holostomum. 



(3.) The determination of the anatomy and histology of this adult form. 



(4. ) The development of the eggs through the earlier stages of segmentation 

 toward the formation of a ciliated embyro. 



(5.) The correct placing of two forms (the larval and the adult) in the sys- 

 tematic arrangement of the trematodes. 



[The detailed accounts of these observations, together with the drawings of 

 all the structures described, are intended to appear in a published report later.] 



