THE CELL ASTER ' 485 



needle is bent at right angles so that it can be brought into a 

 drop hanging from the roof of the chamber. In the drop are 

 the cells to be dissected. 



Marine eggs were selected whose development could be easily 

 followed so as to determine their post operative viability. The 

 eggs of Echinarachnius and of Cerebratulus lend themselves 

 well for operative work, that of Echinarachnius because of its 

 beautiful transparency and that of Cerebratulus because of its 

 comparatively high resistance to injury. In Echinarachnius 

 the presence of red chromatophores, sparsely scattered through- 

 out the jelly surrounding the egg, is not enough to disturb one's 

 view and the jelly and fertilization membrane are too soft and 

 extensile, during very early segmentation periods, to afford any 

 hindrance to the microdissection needle. The Cerebratulus egg 

 is rather opaque and the egg membrane which rises off the surface 

 of the egg when placed in sea water is comparatively tough. 

 The membrane, however, can be easily removed by passing the 

 eggs, which have stood in water for twenty minutes to one-half 

 an hour, through a fine cambric cloth. It was also found that the 

 eggs could be considerably flattened during cell division, so that 

 the various cell structures are spread out in a broad, com- 

 paratively shallow area and the asters form with rays very long 

 in the plane of flattening and very short in other directions. 

 This offers a distinct advantage for dissection purposes. 



3. Hyaloplasm and hyaloplasm-sphere 



The word hyaloplasm is used in this paper to designate the 

 continuous hyaline ground substance of protoplasm in which 

 granules (the microsomes and macrosomes or alveolar spheres 

 of Wilson) are embedded This use of the word hyaloplasm, 

 as applied to the interalveolar material of Biitschli's proto- 

 plasmic foam, is urged by Wilson ('01 a, b.) because of its priority 

 and also because it is purely descriptive and introduces no 

 theoretic implications. 



The word hyaloplasm-sphere (Wilson, '01) is given to the 

 central transparent area of the aster from which the astral rays 

 radiate. In fixed material Wilson describes this area as includ- 



