The Life History of Tillina Magna 425 



baum, Boveri and others have estabhshed long ago, the fact that 

 growth and differentiation cannot take place without the presence 

 of both materials. There has been some evidence that the nucleus 

 actually gives up some of its chromatic material to Protozoa, also 

 in the maturation processes of the egg. Lillie ('02) finds somewhat 

 similar evidence in the developing egg of Chaetopterus. In the 

 preparation for the division into two cells, there is a definite flowing 

 of nuclear material into the cytoplasm, to become the granules of 

 the endoplasm. Also in eggs differentiating without cleavage, 

 he finds a definite relation between the microsomes of the cyto- 

 plasm and the chromatin of the nucleus, the one originating from 

 the other. These are eggs in an abnormal condition, yet it is of 

 value to find the same processes taking place under forced condi- 

 tions as in the natural development. Even in Tillina, two instances 

 were found where there seemed to be a breaking down of the 

 nuclear membrane at one point, allowing the nuclear material to 

 mingle with the cytoplasm. The individuals were not in an abnor- 

 mal condition, on the contrary, they were taken at a time of rela- 

 tively high activity, a condition not to be explained by the theory 

 that the nucleus had become too large in relation to the size of 

 the cell, and was regulating itself by this means. 



Boveri ('05) offers what might be considered evidence for Hert- 

 wig's theory, namely, that in his experimental studies on larvae, 

 he finds the cell volume to be proportional to the number of chro- 

 mosomes, and the number of cells proportional to the chromosomal 

 mass, thus the size of the nucleus would seem to determine that 

 of the cell. He adds, however, that a certain quality as well as 

 quantity of nuclear material is needed to bring about the most 

 favorable results. 



Minot in his recent book "Age, Growth and Death" has ad- 

 vanced a theory somewhat similar to that of Hertwig. In brief, 

 he believes that the segmentation of the ovum is a process of rejuv- 

 enation, that is, the ovum must be considered an old cell with an 

 excess of protoplasmic material. In order to regain the proper 

 balance between the nuclear and cell size, segmentation takes 

 place, young cells are produced and the nuclear material is in- 

 creased at the expense of the protoplasm. When this process 



