2 DEAN. [Vol. XI. 



factorily understood. Every investigator who has been fortu- 

 nate enough to secure the spawning fish, seems to have either 

 failed in completing his material of developmental stages, or by 

 faulty methods of preserving it has been unable to carry out a 

 detailed study. The Sturgeon has not unnaturally been made 

 an object of national investigation by Russians, and our present 

 knowledge of its early development is to be obtained only in 

 the more detailed works, in Russian, of Salensky ('77-'8l) and 

 Peltsam ('87). In Germany the studies of v. Kupffer ('91) on 

 Acipenser were based upon material which unfortunately was 

 lacking in younger stages. Of Lepidosteus embryonic stages, 

 as is well known, have been obtained by different investi- 

 gators five or six times, and within comparatively recent years: 

 it has been owing mainly to technical difficulties that little has 

 yet been published of its earlier developmental history. 



In the following paper it is the writer's object to describe 

 the early development of Gar-pike and Sturgeon, and by ex- 

 amination of these forms side by side to permit more definite 

 comparisons as to the mode of development of Ganoids. 



The material for the study of Acipenser was obtained by the 

 writer during the spring of 1893 at Delaware City, Del., and 

 has afforded a satisfactory and well-preserved series of general 

 developmental stages. The mode of acquiring it has been 

 already recorded ^ ; spawning fish were taken several times 

 during the writer's visit, and a number of experiments were 

 made to determine a successful mode of artificially fertilizing 

 the eggs, and a practical method of hatching them. As a 

 result of the experiments it became possible to obtain an abund- 

 ant supply of embryos, and considerable care was taken both to 

 secure as perfect a set of the developmental stages as possible, 

 and to preserve them in several reliable ways. As a fixing 

 agent, the picro-sulphuric mixture should be mentioned as hav- 

 ing proven in the main most satisfactory for sectioning. The 

 developmental stages of Lepidosteus, as will be noted, were 

 recently obtained during a visit to Black Lake, St. Lawrence 

 Co., N. Y., made in company with Prof. E. B. Wilson, of 



1 Dean : Sturgeon Hatching on the Delaware. U. S. F. C. Bulletin, 1893, 

 No. xviii. 



