The Developnieiit of the Heart in Shad. 219 



following objections to the use of the words pelagic and demersal 

 in a morphological sense will sufficiently indicate their unsuitability. 



(a) Their use, in this sense, is apt to entail the statement that 

 a given egg is either demersal in habit and pelagic in structure, 

 or vice versa, which is undesirable. 



(&) N"either of these terms can be used to express the structure of 

 a viviparous egg. 



(c) These terms, as strictly applied, have no more morphological 

 significance than has the term viviparous itself. 



Statement of the object in investigating the development of the 

 heart in shad, and of the scope of this investigation. 



The development of the heart in embryos of Type 2 has received 

 a large share of attention, particularly in Salmo and allied genera 

 in which the process of heart-formation has been definitely made out. 



The heart in embryos of Type 1 differs considerably from that in 

 embryos of Type 2, particularly in its relation to the vascular 

 system of the yolk. The development of the heart, however, appears 

 to have received somewhat scant notice. Ryder has given a brief 

 account of some of the changes undergone by the heart in Gadus 

 morrhua (callarias ), '82, and in Clupea (Alosa) sapadissima, '85; 

 Boeke has described the early development of the heart in Mursena 

 (endocardium particularly), '03. There are also some earlier in- 

 vestigations, dealing with the living embryo alone, which, necessarily, 

 leave much to be desired. 



It has been attempted here to give a consecutive account of the 

 development of the heart in shad, as representing Type 1, from the 

 earliest possible stage until the adult arrangement is recognizable. 



Material and Methods. 



The material investigated, the property of The Wistar Institute of 

 Anatomy, Philadelphia, was collected during the seasons 1905, '06, 

 and '07 at the hatchery of the Pennsylvania State Fish Commission, 

 Torresdale, Pa. To the Commissioner, Mr. W. J. Meehan, I hereby 

 tender my thanks for his many courtesies. 



Prior to a period of development at which the embryo is capable of 



