10 Art. 3.— Naohide Yatsu : 



cutting was accompanied with some difficulty. Very soon after 

 the operation the cut surfaces close ; so rapid is the closure that 

 one cannot, as a matter of fact, see exposed entoplasm(f/. Maas 

 '03 p. 45). Each of the eggs operated on was placed in a 

 compressorium\ and the subsequent progress of cleavage was 

 followed. From a single egg several sketches of successive 

 stages were made. In the plates of the present paper in most 

 cases only the first and the last stages have been reproduced, 

 since the intervening ones would l)e of little value in ihustrating 

 the following experiments. 



a) Experitiiciit 1 (four cases). 



A portion uf the egg was cut below tlie " cleavage head " at 

 various angles and along various levels, and the enucleated pieces 

 were watched to see if they showed any sign of division activitv-' 

 Even in the case in which the cutting plane passed very near the 

 " cleavage head," nothing happened in the enucleated piece — it 

 simply rounded up and ceased to develop further (PI. Ill, Fig. ol). 



1)) Expciiment II (one case). 



The above experiment was modified in tlie following waj'. 

 An incision extending two thirds of the diameter of the egg was 

 made below the "cleavage head" to see if the connection with 

 the nucleated part of the egg would impart some division activity 

 (PL III, Fig. 32). The cleavage went on normally, cutting the 

 upper part in two, but the lower past remained undivided (PL III, 

 Fig. 33). 



The above two experiments (Exp. I and Exp. II) clearly show 

 that portions devoid of the " cleavage head " do not manifest any 

 division activity whatever. 



1 This was not used for compressin.,' the eggs but as a sort of live-box for keeping theui 

 alive. 



2 I have a case in which both pieces produced by a horizontal cut cleaved. It can hardly 

 be doubted that it was a dispermic egg. 



