274 LILLIE. 



so to speak, from a large number of active ones ; as Morgan's, 1 

 that any considerable area in the sea-urchin egg may produce 

 an aster, and I may add a centrosome, under the stimulus of 

 abnormal salt content of the sea water ; or Mead's 2 observa- 

 tions in the same direction in Chaetopterus ; or Conklin's 2 

 observations on the egg of Crepidula, similar to mine ; or of 

 the observations of Strasburger 3 and pupils that karyokinesis 

 in vegetable tissues does not necessarily imply the presence of 

 centrosomes at the poles of the spindle, as it does not in the 

 maturation of Ascaris or of Molgula 3 (Crampton). 



UNIVERSITY OF MICHIGAN. 

 January 6, 1898. 



1 Morgan, T. H., "The Production of Artificial Astrospheres," Archiv f. Ent- 

 wickelungsmechanik dcr Organismen. Bd. iii, Heft 3. 1896. See also report 

 in Science ('98) of the meeting of the American Morphologists in Ithaca in 

 December, 1897. 



2 See report in Science ('98) of the meeting of the American Morphologists 

 in Ithaca in December, 1897. 



3 Jahrb. wiss. Bot. Bd. xxx. 



