502 



Mr. C. Shearer. On the Existence of [Jan. 30, 



blastomeres of Strongylocentrotus eggs, which had been preserved first in 

 weak and then in strong alcohol. These threads seem to be outside the cell 

 membrane as far as one can judge from his figs. 14 and 16. They look not 

 unlike coagulation artifacts, and it is doubtful if they are really protoplasmic in 

 nature. 



Hammer (4) has recently described bridges of protoplasm that connect 

 blastomeres at the ends of their planes of contact. These are most obvious 

 in the two-cell stage, a delicate bridge joins the blastomeres at each 

 end of the cleavage plane. I have frequently observed these connec- 

 tions on the eggs of Pomatoceros where they are well marked. But the 

 best examples are furnished by the eggs of Phoronis. In the two-cell stage 

 they are plainly evident, and on the living egg one can readily trace with the 

 high power of the microscope, protoplasmic granules continuously from one 

 cell to the other through these bridges. Klaatsch(6) has described some- 

 what similar connections, on the egg of AmpMoxus, though he represents 

 bridges connecting the cells along the course of the cleavage planes as well. 

 In the gastrula of AmpMoxus he shows all the cells connected by delicate lines. 

 They however look not unlike the result of shrinkage during preservation. 



Both Hammer and Klaatsch discuss the possible influence of these cell 

 communications in co-ordinating the activities of the individual cells. The 

 results of experimental embryology of the last decade amply show that such 

 influence must exist, and that it is impossible to hold that in the growing 

 organism the cell lives an isolated existence. Wilson (16) in speaking of 

 the results of his work on the mechanical separation of the blastomeres of 

 AmpMoxus, states, " There must be a structural continuity from cell to cell 

 that is the medium of co-ordination," and that it is this that "is broken 

 by mechanical displacements of the blastomeres." 



Townsend (12), has shown how in plants very delicate strands can 

 transmit the influence of the nucleus from cell to cell. In the plasmo- 

 lysed root-hairs of Marchantia the protoplasm is broken up into balls, 

 some of which only are nucleated, the nucleated portions alone are 

 capable of utilising the starch they contain and of surrounding them- 

 selves with a new cell wall. But some of the non-nucleated portions are 

 sometimes connected with a nucleate portion by long delicate strands or 

 threads, they then, as the result of this connection with the nucleus, elaborate 

 cell walls ; if this strand is however broken they lose this power and soon die. 

 While it is well known that the nucleus plays the essential part in the 

 formation of new products chemical or morphological of the cytoplasm, it is 

 remarkable to find this power capable of being transmitted from one mass of 

 protoplasm to another, or as in the case of the leaf-hairs of Cucurbita, from 



