EXPERIMENTS \VJTH CHRYSOMELID BEETLES. 21 



the case of the sea-urchin egg, has actually been measured, though 

 not enough experiments were performed to make the resultant 

 figures of much value (Spaulding, 1907). 



The eggs of chrysomelid beetles differ in several respects from 

 any thu- t'.ir u-ed for \\eight experiments. In the first place they 

 an- < overed l>y a <hitinou- chorion which is comparatively im- 

 pervious to fluid-, and i- ially well adapted to with-tand 



desiccation. The method of cleavage, /. e., superficial, dii't'ers 

 from that of tli. 'Heretofore examined. 



The rc-nlt- .( the t\\o -eric- of \\eighings recorded in Tables 

 I . and II. prove conclusively that there is a loss in weight, and 

 thai this loss is largely due to evaporation. A comparison of the 



data in Table- I. and II. -lm\\- thi- quite clearly, since the i 

 \\ei-h"d in Table 1 . \\ ci c allo\\ ed tO develop Without the addition 

 of moisture, and < on-equentK d. .1 in weight more rapidly. 



2. 7 'In A'I/'I and Adults. 



Method nml l>,it<i. The tuenty l.u\a that hatched from the 

 n-c(| in del. -i mining the lo in \\iijn of developing < 

 I able 1 I were \\eiijicd lail\ until tlu-\ |>upated ; the pupa' 

 \\ere then \\eiijicd dail\ . and I'm. illy the adults. These wei'Jim^- 

 extended over the peri.-d from Juls i: to August 14, 1908. 

 I'-c. .HIM ..| (he i|ail\ di-turbaiice- made neee ary by the \\ciijl- 

 . in.inx .'! the lai \ a- die<|. "I" hi- mortalit\ \\ as great e-t during 

 the lir-t lour da\-; ho\\e\er, under normal n mditions, main of 

 the lai \ a- die during thi- earl\ 



'fhe data obtained ha\ e been arraiued chronologically in Table 



III. 1:^ i gives the curve showing the dail) increase in weight 



and l-'ig. j i^i\c- the curve -ho\\iu- i he daily percentage iiu ie- 

 nu-nt- in \\ci-ht. 



/'/x /<.v.v/o;; mid i'i>ni'lnsinns. The |)roblem of growth i- one of 



t intere-t to /.Milo^i-t-. and its Study has been gixt'ii added 



im|>etus b\ the \\oik <>t Minoi I^MI. 1907). Thi> in\ e-ti^ator 



considered -ro\\th not as in increase in -i/c or \olnme, but as 



an increa-e in ma or \\cijn . The rate of growth was measured 



b\ him b\ taking the incrca-e in \\eight during a definite period 

 and e\|u-i' ing it as a percentage o| ilu- \\eight at the beginning 

 of that period. Any change in weight can thus be -hown by 

 successive percentages for equal period- of time. 



