LIMITS OF DIVISIBILITY OF LIVING MATTER. 59 



Up to the 



group c of Fig. i, containing the micromeres, formed an 

 irregular mass of cells c, Fig. 2. The protoplasm d inside 

 the membrane formed, as 

 usual, one blastula d, Fig. 

 2. The following morning 

 the blastula d, Fig. 2, that 

 contained a little more sub- 

 stance than both the blas- 

 tulae a and b together, had 

 been transformed into a gas- 

 trula, d, Fig. 3, while a and 



b remained blastulae ; c was a mass of detritus, 

 blastula stage the smaller pieces, as a rule, developed at the 

 same rate as the normal ova, but when the blastula stage was 



reached, either they 

 stopped developing 

 altogether, or the de- 

 velopment went on 

 more slowly. Thus 

 the larger piece d 

 went into the gas- 

 trula stage, while the 

 smaller pieces a and b were still in the blastula stage. I do 

 not wish to go into too many details here, as I shall deal with 

 the same phenomena more explicitly at another place. One 

 word may, perhaps, be added concerning such irregular masses 

 of cells as c, Fig. 2. They formed, on their outer surface, 

 cilia like normal embryos, and whirled through the water quite 

 as rapidly and lived often as long as normal Plutei, but no dif- 

 ferentiation of organs took place. They reminded one of those 

 tumors, the so-called teratomes, which so puzzle pathologists,' 

 and which are believed by some to be remnants of embryonic 

 tissue. They appeared, indeed, like free-living teratomes. 



4. In all these experiments the smallest Pluteus ever observed 

 was about one-eighth the mass of a Pluteus from a normal egg 

 of the same culture. Before drawing from this fact any 

 conclusion concerning the limits of the divisibility of living 

 substance it is necessary to be sure whether such a Pluteus 



FIG. 3. 



