540 R. fV. Hegrier 



similar length of time, but the yolk-globules have a distribution 

 almost exactly like that induced in the latter. Many of the eggs 

 were allowed to develop; all of these hatched in six days. 



Series L.D. m 



■ The same beetle as that of Series L.D. / laid a batch of eggs 

 at 7 p.m. July 19, i.e.y fifty-one hours after she was centrifuged or 

 thirty-three and one-half hours after the first lot were deposited. 

 No effects of centrifugal force could be discovered in sections of 

 these eggs. Normal larvae hatched from those eggs which were 

 not preserved. 



Series L.D. 



A third batch of eggs were laid by the beetle of L.D. / at i p.m. 

 July 20. The preserved eggs showed no effects of centrifugal force ; 

 the others hatched in six days. 



Series L. D. q 



A fourth lot of eggs were laid by the same beetle as in L.D. / on 

 July 22. These agreed in every respect with those described in 

 Series L.D. m. 



IX REVIEW OF THE EFFECTS OF CENTRIFUGAL FORCE UPON 

 DEVELOPING EGGS 



I Distribution of the Egg Contents 



The most noticeable result obtained by centrifugal force is the 

 redistribution of the materials contained in the egg because of the 

 differences in their specific gravities. A number of cases have 

 been reported of eggs whose contents are normally visibly different 

 and localized in particular regions. For example, Boveri ('01, a, p. 

 145, Fig. I, and '01,^, Taf. 48 and 49, Figs. 6-22) found three hori- 

 zontal zones present in both unfertilized and fertilized eggs of 

 Strongylocentrotus lividus. These zones could still be recognized 

 in young blastulae. Wilson ('04, p. 68) states that, "TheDenta- 

 lium egg shows from the beginning three horizontal zones, an 

 equatorial pigment-zone and two white polar areas. Each of the 



