Experimental Studies on Germinal Localization. 53 



change begins with the formation of a fourth lobe, com- 

 posed of white material, which is at first much smaller than 

 any of the preceding (94h, 46 minutes after 94g). Unlike the 

 preceding lobes this one was not resorbed into the fragment, but 

 was permanent, slowly increasing in size until after two or three 

 hours it was nearly as large as the remaining portions, the frag- 

 ment now appearing as if divided into two (94i). 



This case is fairly typical of several that were followed through 

 the entire cycle of changes, and one or more of the stages were 

 seen in many individuals. The lobes are not always so distinctly 

 formed as in the one figured, and the final stage, though usually 

 like that described, varies considerably in appearance. 



{b) Behavior of the isolated polar lobe. — Previous to mak- 

 ing the observations just described, I had several .times observed 

 changes of form in the isolated polar lobes after their removal 

 from the trefoil stage. On reexamining the matter I found that 

 these changes are also periodic, taking place approximately at the 

 same time as the cleavage in the lobeless nucleated portion. The ac- 

 tivities of the isolated lobe at these periods vary considerably in 

 different individuals. Sometimes the activity is no more than a 

 slight change of form, the spherical lobe becoming slightly pyri- 

 form or even almost amoeboid. Frequently, however, the isolated 

 lobe actually forms a smaller lobe by a process that closely sim- 

 ulates the formation of a polar lobe by a whole egg or an egg- 

 fragment. In any case, each period of activity is followed by a 

 spherical resting-stage that coincides approximately in time with 

 the resting stages of the segmenting lobeless portion. I regret 

 that I had not time to study this remarkable phenomenon with 

 sufl[icient care, but give series of sketches illustrating two particular 

 cases. Fig. 97a shows a lobe soon after its removal; 97b, the 

 same, 16 minutes later just after the egg had divided into four; 

 97c, the ensuing resting stage, 14 minutes after 97b; a second 

 period of activity followed, in which the lobe again constricted, 

 but not so deeply as at 97b, followed by a second spherical stage; 

 97d and 97e show the third active period, and 97f the final result, 

 after which no further change occurred. In 98 is shown the final 

 active period of a lobe, which resulted in the permanent apparent 



