52 



MEMOIRS OF THE NEW YORK ACADEMY OF SCIENCES 



II. KUPFFER'S VESICLE. 



The Prevailing View. In the present paper I cannot enter into a complete 

 historical review of this subject. KUPFFER'S own conception of this structure we 

 shall consider later. In the meantime, I shall state briefly the accounts given by 

 AGASSIZ and WHITMAN ('84) who first satisfactorily described the condition in the 

 pelagic type of egg and by HENNEGUY ('88) who was a pioneer worker in this line 

 upon the trout. AGASSIZ and WHITMAN observed in the pelagic egg of Ctenolabrus, 

 a number of small vacuoles, appearing in the periblast beneath this region of the 

 embryo. These vacuoles soon united into one (so much had already been observed 

 by KINGSLEY and CONN, '83) and above it the cells of the embryo began to arrange 

 themselves as a columnar epithelium which arched over this cavity. In the case of 

 the trout embryo, HENNEGUY states that the formation of the vesicle is preceded by 



FIGURE 7. 



FIOUKE 8. 



Section showing fully formed Kupffer's 

 Vesicle in the trout (after Henneguy). 



KV. 



Embryo of Clenolabrus, showing fully formed Kupf- 

 fer's Vesicle. Kv, |Kupfer's Vesicle, GHy, gut-hypo- 

 blast. 



a radial arrangement of certain cells in the posterior undifferentiated region of the 

 embryo. A cavity then forms in the midst of these cells, thus giving rise to the 

 vesicle. 



Figure 8 is drawn from one of my own preparations of Cienolahrws. AGASSIZ 

 and WHITMAN give no satisfactory figures, although their description is clear. 

 Figure 7 is taken from HENNEGUY'S paper on the trout. Both of these figures 

 represent the vesicle in its fully developed condition. They differ in that the vesicle 

 of the trout is from the first completely bounded by cells, while in the pelagic egg 

 the cellular wall is not complete. But the accounts agree in representing the waP 

 of the vesicle as differentiating in situ from a homogeneous mass of cells without 

 reference to any preexisting (cellular) structure. 



It is now well established that both types of Kupffer's Vesicle as above figured 

 actually occur : the question as to which type is more primitive will be considered 

 later. Both of the above accounts, although true as far as they go, are incomplete 



