CLEAVAGE OF LEPIDOSIREX 



501 



one continuous furrow cutting across the meridional furrow ; 

 while on the other half of the egg (Text -fig. 6, lower half) two 

 small furrows, likewise vertical, are just beginning to develop, 



Text-fig. 5. 



Nucleus of segmenting egg of Le pi do siren in early stage of 

 mitosis. The nucleus was traced in outline under a Zeiss I" 

 homogeneous immersion objective with ocular 18, and then 

 worked up in detail under 3 mm. apochromatic homogeneous 

 immersion ' objective with Bitumi binocular eye-piece. An 

 attempt has been made to bring out the stereoscopic relief of the 

 original by shading the nucleus as if it were isolated. 



The divisions of the scale represent hundredths of a millimetre. 



taking their origin however from the other meridional furrow 

 than that from which the first two started. 



In the fourth egg at this stage the segmentation furrows at 



