1897.] Hammar’s Ectoplasmie Layer. 1031 
Figure 4 indicates the difference between the two modes of 
intercellular connection as seen in preserved material, where, 
however, the threads are fewer, thicker and otherwise altered 
by the Killing fluid and by subsequent treatment. Be- 
neath the outer film of connecting substance and on various 
levels, (some quite far down), very definite protoplasm-like 
threads extend out from a cell and crossing the cleavage cav- 
ity become continuous with the surface of some other cell. 
These filaments have a characteristic shape, mode of origin, 
_ Insertion, structure and size. They are the altered remnants 
and representatives of the living filaments seen in the live egg. 
Besides the long filaments the specimen shows pseudopodia- 
like processes or tufts of threads, arising from-one of the four 
cells. These came upward toward the membrane-like ex- 
panse and seemed to be continuous with it, so that the filament- 
ous substance and the filmy expanse appeared to have been 
one common material. 
In life the filaments are subject to flow and to change, and 
the same may be true of the ectosarcal expanse. 
Though the filamentous and the membranous connections 
of cleaving cells seem so different, it is not improbable that 
they are both expressions of the same contractile powers in the 
ectosarcal part of the egg cell, and they both serve to make the 
living material continuous from one cell to another. 
In the living eggs of representatives of widely separated 
groups of animals we thus see reasons for believing that the pro- 
cess of cleavage does not isolate the cells as much as'has been 
thought; either the cells remain connected from the first and 
are but areas in a common mass of living material, or they 
may make and break connection with one another by living 
filaments, formed as fast as cleavage tends to organize the egg 
into cell areas. In preserved material we see remnants of such 
connections, and it becomes probable that such connections 
will be found throughout the animal series. 
With the ever increasing knowledge of intercellular bridges 
in animals and in plants, and the recently demonstrated fact 
that in Echinoderms these bridges are used as means of trans- 
portation, that the filaments allow material to pass from one 
