CELL BEHAVIOR IX TISSUE CULTURES. 259 



wanting in the earlier stages. Dr. Dederer's observations have 

 shown the close relation between epithelial cells and the fan cells 

 and it is then not improbable that this layer contains the fan 

 cells. Moreover she has shown these fan cells to be necessary 

 for the spreading of the epithelial growth l>y attaching it to the 

 rover glass. Therefore the absence of the epithelium in cultures 

 from the younger embryo-; may be due to the absence of this 

 sub-epithelial layer with its included fan cell-. 



In a few cultures other impumented cells of presumably mes- 

 enchymul origin and of exceedingly irregular form were noted. 

 Tlu-ir mode of motion -reined typically amoeboid. 



Tai'tili- I ns. The tactile reactions of various types nf 



"ell- were, studied. For this purpose the Cells were touched with 

 a delicate 1.1 die moved by a Barber mien t-di--cct i< >n ap- 



paratUS. It" the body of a double fanned Cell -uch a- that sho\vn 

 in 1 i : _ .} i~ sharply stimulated the fans are rule ised iiid the whole 

 cell Contracts, becoming spheri< J. A fail may be pried loo-e. and 

 a similar reaction en-iies. The contraction seem- in part due to 

 an ela-tic ten-ion of the cell. I have not found it possible to 

 stimulate a < ell b\ toiichr i partially mutil.itiiu -i -mall 



portion of the fan I .pla-m does not -eem to conduct a 



stimuli!-. In -.-me ie stimuli!- near the boundary of 



a fan and the cell -talk of a greatly elongated cell will call-c . oiu- 

 plete contra tii'ii. The material of the fan -eem- (< flow to- 

 gether, making a ball of protupla-m which i- carried along with 

 the -t. ilk to the center of the cell. 



I ha\e tried a few experiment- to determine the chemutactic 

 response "f -u<-h ti ue cell-. A .loud of methylcne blue in- 

 jected by a mi T"-pipette will cau-e the contraction <,f the-e 

 i-olated cells. I ha\e not -ucceeded in obtaining an\' more def- 

 inite respon-e such a- a change in the direction of motion. 



Previous writers, Bancroft ('12), Stockard ('15' and \e\vmann 

 ('18) ha\e dc-cribcd two t\ pes of chroinatophores in the Fnndithts 

 embryo. These are black chromatophores or melauophie- and 

 the brown (or red) chromatophores. Bancroft ('u ha- de-cribcd 

 a third type which also appeared in these tissue cultun Th* 

 were \cllo\v and -mailer than the other types and -iiowed few or 

 no pseudopodia. As a group, the chromatophores are but -lightly 

 responsive to tactile stimulation. If a needle is pushed a 



