1890.] 1 0€ » [Ryder. 



2. The law pointed out by Leuckart and Spencer that beyond the sixth 

 dimension above unity mass outruns surface, may be regarded as in some 

 way operative in hindering the growth of cells, through cumulative inte- 

 gration, beyond certain dimensions, in order that they may carry on res- 

 piration, nutrition, in a word, metabolism, most efficiently, under ordi- 

 nary cosmical conditions. The average of cellular dimensions varies in 

 different forms. So does the molecular constitution of living matter, giv- 

 ing rise to idioplasms. 



3. The continuity of growth is maintained through cumulative integra- 

 tion, the continuous reduction in mass of "living" matter is effected 

 through segmentation in some self-regulated way, presumably according 

 to the Leuckart-Spencer principle. 



4. The growth of the lowest forms of living beings is effected in the main 

 or ends principally in the production of a single kind of living matter. 

 In higher forms, in which the cells are also generally much larger, two 

 kinds of living matter are developed in very unequal proportions. In the 

 first case when division occurs, due to growth, there is little or no reaction 

 between the two kinds of living cellular substance and division is direct 

 or without karyokinesis. In the second case there is a reaction between 

 the two kinds of living matter which is expressed most strongly as kary- 

 okinesis, or nuclear motion on the one hand and the development of 

 fibres on the other radiating from or converging upon the nucleus. 



5. The effect of cumulative growth of the cell-mass has been to finally 

 produce a preponderating quantity of plasma which invests the primitive 

 nuclear plasma or chromatin with a thick envelope ; this envelope is 

 known as the cell-body or cytoplasm, and also provides afield or space in 

 which the action and reaction of the two kinds of living matter found in 

 the cells of higher forms may display itself as karyokinesis. The plasmic 

 space in which this occurs may be called a cytoplasmic field. 



6. The action and reaction between the two kinds of plasma controls 

 the order and direction in which the phenomena of growth take place, 

 but in conformity to certain dimensions and earlier relations of the cyto- 

 plasmic field to its sources of nourishment. 



7. The effect of the forces at work in cumulative integration is to aug- 

 ment mass, the effect of the action of segmentation so as to effect a read- 

 justment according to the Leuckart-Spencer principle, is to bring about 

 discontinuity of growth or reproduction through fission. 



8. The asexual method of reproduction seems to have been purely a 

 consequence of the operation of forces under the laws of cumulative inte- 

 gration and the law of Leuckart and Spencer, under varying conditions, 

 and to have led to a continuously repeated division of living matter, as 

 fast as it was formed into small masses, through direct processes of fission, 

 composed at first almost wholly of nucleoplasm or chromatin. 



PROC. AMER. PHILOS. SOC. XXVIII. 132. T. PRINTED MAY 28, 1890. 



