Observations and Experiments on the, Ctenophoro Eg^. Xq 



This experiment streiigtheiis the results obtained from tho 

 preceding one (Exp. Ill); that is, the nucleus, centrosome, and 

 the amount of cytoplasni above the cutting plane have little to da 

 with the growth and direction of the cleavage fuiTOw\ 



; e) Experiment V (One case). 



To slightly modify the above experiment, the cut w^as extend- 

 ed to the middle of the nucleated part as is shown in Fig. 47 (PL 

 IV). The "cleavage head" came down unintemipted by the 

 operation. But the cleavage furrow stopped at a certain point 

 (PI. IV, Fig. 48) OAving probably to the fact that the nuclei had 

 already enterd the phases of the second cleavage. 



f) Experunent VI (Seven cases). 



Id tlris experiment the "cleavage head " were split in two 

 at various stages by a vertical cut to see if the furrow proceeds 

 from the end of the cut or from some other place. 



In no cases were two "cleavage heads" formed. In one case 

 out of seven the cleavage furrow made its appearance at the bottom 

 of the incision, dividing the egg in two equal blastomeres. 



In the six cases a remarkable phenomenon was met with. A 

 new " cleavage head " emerged on one side of the incision below 

 the original bottom of the furrow and in most cases a little above 

 the end of the cut. It proceeded almost at right angles to the old 

 cleavage plane. The portion of the cut below the new cleavage 

 furrow dwindled and was either obliterated entirely or remained as 

 a hole for a fairly long time. In Fig. 49 (PI. IV) the operation was 

 made when the cleavage furrow was very shallow,' and the result 

 was Fig. 50 (PI. IV). In passing, it may be remarked that in the 

 egg of Pennaria Hargitt ('00) observed a similar figure (his 



PL II, Fig. 2). 



It is interesting to note that in this case an ectoj)lasmic t hiclvc n- 

 ing was foomed at the side of the egg (PL IV, Fig. 50). ^^Vhen the 



1 'i'he original bottom of tbe cleavage furrow is marked with X X ia this and the- 

 following figures. 



