STUDIES OF REPRODUCTIVE ELEMENTS: IL ^99 



(Figs. 5-0). Which of the two nuclei goes into the one half and 

 which into the other, is not easy to ascertain, as a narrow line of 

 cytoplasm, as above stated, now stretches also in front of the nucleus 

 nearly in the same manner as does the Staborgan behind, so that the 

 fore and hind ends are difficult to distinguish. But in all ascertained 

 cases, the front nucleus o-oes into the rio^ht side and the hinder one 

 into the left. All the while the archoplasm remains close to the 

 nucleus. The line of division gradually extends both ways towards 

 opposite surfaces of the body, and the animal assumes the well-known 

 biscuit-shape. Meanwhile, the two protoplasmic masses with their 

 respective nucleus and archoplasm shift their positions and come to lie 

 on each .side of the line of division, nearly opposite to each other (Fig. 

 9) ; so that division of the animal now appears to take place in the 

 longitudinal plane. The relative position of the nucleus and the 

 archoplasm does not seem to remain the same during the earlier stages 

 of the division, (Figs. 5-9), but at later stages the former lies farther 

 away from the dividing line (Figs. 10-12). 



The time during which all these changes take place, from the 

 stage shown in Fig. 3 to the stage of Fig. 9, varies greatly in 

 different individuals ; but from observations upon fourteen animals 

 kept in a moist chamber at the Misaki station, during the latter 

 part of August 1893, the time required varies from six to eight 

 hours. 



The division of the body proceeds, until only a small connecting 

 bridge of cytoplasm is left (Figs. 10 and 11). During this stage, tenta- 

 cles usually grow on both halves, which swim together like the 

 Siamese twins. Such a couple, with rather short tentacles, is shown 

 in Fig. 11. That shown in Fig. 12 has tentacles nmch more developed. 

 This figure is drawn from a living specimen, so that the nuclei (//) 

 appear quite transparent, while both the archoplasms (a) are seen as 



