230 PAULINE H. DEDERER. 



nuclei, however, were common in ectoderm cells (Fig. 8), as 

 were also nuclei partly constricted into two, or with several 

 irregular constrictions and variable nucleoli. There is no reason 

 to believe that this condition is followed by division of the cells. 

 It may be that the nuclei fuse together again, as Macklin ('16) 

 observed in tissue cultures of the chick, and that the cells sub- 

 sequently divide by mitosis. Holmes ('13) observed amitosis 

 of the nuclei in t : ssue cultures of various tadpoles, but he states 

 that nuclear division was not followed by division of the cyto- 

 plasm. 



A few mesenchyme cells were observed to divide by mitosis 

 and several groups of chromosomes in metaphase appeared in 

 the stained material. Bi-lobed and double nuclei, indicative of 

 amitosis, were also observed (Fig. 9). 



Cultures of Chick and Fundulus. A piece of fundulus tissue 

 and a piece of muscle tissue from a chick embryo of eight days' 

 \ncubation were -placed together in a drop of Locke's solution 

 containing chicken bouillon, and kept at 39 C. At the end of 

 48 hours each piece showed its characteristic form of growth, the 

 fundulus having the double membrane previously described, the 

 chick tissue showing the usual radiating type of outgrowth. In 

 one region the fundulus outgrowth could be seen growing over a 

 portion of the chick explant as over a foreign body. In another 

 region outgrowths from the two pieces were almost in contact, 

 but the cells from the two explants showed no tendency to 

 intermingle. Specific differences were observable within the 

 cells. Mitochondria are much more abundant in the chick 

 tissues and the cytoplasm appears to be different, as shown by 

 the greater ease with which the cellular structures of the chick 

 may be observed. 



General Considerations on the Movements of Membrane Cells. 

 The behavior of the cells in the cultures at different times is of 

 considerable interest. Taking the normal form of the ectoderm 

 cells as a standard, we find that the cohesive property of these 

 cells is increased suddenly at the time the cut is made, as shown 

 by the rounding up of the cells. The stimulus of the injury was 

 sometimes effective for several hours. This influence seemed to 



