- 



EXPERIMENTS ON THE EGGS OF CHyETOPTERUS 

 AND ASTERIAS IN WHICH THE CHROMATIN 



WAS REMOVED. 



J. F. McCLENDON. 



Last July and August, while in the U. S. Bureau of Fisheries 

 Laboratory at Wood's Hole, Mass., I devised an apparatus for 

 removing blastomeres from ascidian eggs, but as the chorion of 

 these eggs was too tough for a successful operation, I tried to 

 use the apparatus for other purposes. I found that with it I 

 could remove parts of the unsegmented eggs of echinoderms 

 and annelids, and, in the few 

 weeks at my disposal, performed 

 the experiments mentioned be- 

 low. 



THE APPARATUS. 



To a Greenough binocular 

 stand (see accompanying figure) 

 I attached a Spencer mechanical 

 stage supplied with a fine adjust- 

 ment screw (<?) made by Wie- 

 back and Pietzsch, Philadelphia. 

 The addition of this screw al- 

 lowed movement in three dimen- 

 sions, and the fine adjustment (a) 

 carried a tube (^) drawn to a cap- 

 illary opening at the lower end, 

 and with the upper end attached 

 by a rubber tube to the glass tube 

 (r), which I held in my mouth 

 during the operation. The lenses used were Zeiss binocular ob- 

 jective <? 3 and a pair of Zeiss orthomorphic oculars, 4, giving a 

 magnification of 65 diameters. Eggs were placed in 23 mm. 

 depth of sea water in a glass dish on the stage of the microscope 

 and the capillary end of the tube ($) inserted into the water above 



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