E. Warren 2ö9 



If we now (lisreganl the elTect of ecdysis wc can fit a coiitimious curvo to tlie 

 observations. A parabola ot tlic 3rd order is shown in the diagraui, the eiiuatiou 

 to it is : 



y = 9-0807 (109787+ 024.,125.r--005,992.r=+ -000,228.«=], 



where the orif^in is at body-leiif^tli 8 oii workiiig scalc (obsorved cell mean 1027), 

 the vinit of x, or the body-Jeiigth, is five divisioiis of ocular microineter used for 

 body-length, and of (/, or the mean cell-length, five of the divisions of the ocular 

 rnicronieter used for cell-leiigth (see p. 2r)()). 



An exarniiiatiou of this parabola shows us that the regression between size 

 of büdy and size of cell, i.e. the slope of this curve, is very considerable at the 

 youuger pcriods bat that this regression rapidly le.ssens as the animal grows 

 older ; there is also a distinet tendency for a negative regression to occur after the 

 array 72 — 76*. This would mean that up to a certain period of life after the 

 animal has been hatched, the cells of the carapace grow larger as the body grows, 

 and that after this period has been passed the cells on dividing never again attain 

 to such large dimensions. It leads to the question how far the period of life 

 of iiiaximum cell-size is to be regarded as the pei-iod of ma.xiinuni vitality. 



In the development of an animal (excluding the influcnce of yolk) the egg-cell 

 divides into smaller and smaller cells and as the niorula as a whole grows the 

 constituent cells become smaller and the regi'ossion between the size of body and 

 the size of cell is conse(]uently negative. The cells reach a mimmiim size, 

 and then in the developing distomum after a pause the regression becomes 

 positive and the cells attain their maxiinuiii dimensions. Afterwards, in the case 

 of daphnia and perhaps generally, there follows a slight negative regression. 



It would be interesting to ascertain in a .series of forms whether these are 

 general phenomena, and if so, to find the point in the developing embryo at whicli 

 the positive correlation becomes changed into a negative one, also the point of 

 maximum cell-size in the actively growing animal. Perhaps these points might 

 N-ar}' for difterent tissues or organs of the body or they might be nearly uniform 

 throughout the whole body. 



The essential featuie of this preliminary note is to demonstrate the fact of the 

 intimate relationship whicli obtains between the body- as a whole and its con- 

 stituent cells, the mean diameters of the cells change pan passu with the growth 

 of the body. 



There can be no doubt that a wider Statistical stud}' into the subject of 

 cellular characters would yield results of fundamental importance both with 

 regard to the laws of growth, and to our conceptious of the individualitj' of the 

 cell-unit in the body of the living organism. 



* Other curves were tried for graduating the observations, but the graduated valuea found for tliem 

 were remarkably close to the preseut, and they shewed in the sanie way the lilie teudeuey to an ultiniate 

 reduction in cell size. The tcrm regression is here used for the slope of the tangent to the curve which - 

 graduates the relation between body-length and meau cell-size, when we iguore the ecdysis efTects. 



33— '2 



