PROTEOCEPHALUS AMBLOPLITIS LEIDY 193 



SESSIONAL PAPER No. 39b 



in Heidenhain's iron-haematoxylin the oncosphere was seen to be made up of a 

 number of cells packed closely together, whose boundaries were obscure while 

 their nuclei were deeply stained. In living oncospheres each hook was observed 

 to be imbedded in a cone of homogenous material, the apex of which surrounded 

 the proximal end, slightly swollen in this species, while the base at the surface 

 of the oncosphere was about three times the diameter of the distal end of the main 

 shaft of the hook. The tips of the hooks appeared to protrude from the surface 

 of the onocsphere, especially during the phase of separation of the former. 



All of these observations and measurements were made from fresh material 

 in normal physiological saline solution, so that the various stages in the swelling 

 of the outer envelope were not due to osmotic action; this takes place apparently 

 within the uterus as a stage in the development of the egg. 

 • March 3, 1913. 



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