CELL CONSTANCY IN THE GENUS EORHYNCHUS 259 



the accuracy of the results set forth in the following study on cell 

 constancy it should be understood that where a definite number of 

 nuclei is recorded for a given organ that number has been obtained 

 either by careful reconstructions of the part in question or by 

 direct counts of all the nuclei in well cleared toto mounts. In no 

 case has the writer based a strong claim of constancy upon the 

 finding of a similar condition in as small a number as two indi- 

 viduals. In many instances even as high as two hundred individ- 

 uals of the same species have been studied with the greatest care 

 in order to establish the correctness of a finding. 

 , For general results, killing and fixing in saturated aqueous solu- 

 tion of corrosive 'sublimate with about one per cent glacial acetic 

 acid were by far the most satisfactory. Dilute aqueous solution 

 of Ehrlich's acid hematoxylin proved best adapted for staining 

 toto mounts. The chief advantage of this technic over all others 

 consists in the remarkable translucence of the object after mount- 

 ing in balsam. By this method the writer was enabled to study 

 the cytology of even some of the larger forms in toto under a 

 one-twelfth inch oil immersion lens. In the preparation of 

 serial sections the same stain countered with eosin gave good 

 differentiation, but for the finest work iron-hematoxylin was found 

 most reliable. 



5. Cell constancy vs. nuclear constancy 



Since most of the cell walls in the Acanthocephala have dis- 

 appeared, the question arises, whether the consideration of such 

 syncitial structures may be included within the bounds of cell 

 constancy or must be considered under an entirely separate head- 

 ing which might be called nuclear constancy. To the writer the 

 problem finds its solution in the known facts in the embryology of 

 the group. Kaiser has recorded valuable information upon this 

 question of the early development of the Acanthocephala. Re- 

 garding the determinate nature of the cleavage in the group he 

 states ('13, p. 5): "Die Entwicklung der Echinorhynchen ist 

 von der ersten Furchung bis zur Ausbildung des definitiven 

 Wurmes vollig determiniert." Most writers have agreed that 



