308 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the light receptors entirely — the eye-spots which lie on either side of the 

 head, immediately posterior to the base of the antennae. The larvae are 

 positively geotropic. The mealworm's random movements are discussed, 

 and it is shown that the tropism theory, at least in its naive form, can- 

 not be made to apply to its behaviour. Low in the scale as it is, the 

 larva presents highly complex behaviour, the factors of which are but 

 slightly known. 



Development of Agelastica alni.* — Benedykt Fulinski finds that 

 the so-called blastoderm is developed quite in the same way as in other 

 Chrysonielidae, but the ventral portion of the blastodermic epithelium — 

 the germinal ectoderm — forms two lateral plates and a median plate, 

 which are not sharply marked off from one another. The amnion-f olds 

 develop from the germinal ectoderm, and the amnion-cavity precedes 

 gastrulation. In gastrulation there is a true invagination, the middle 

 plate being inturned into the yolk and forming the primary endoderm, 

 which subsequently differentiates into the secondary endoderm and the 

 mesoderm. 



Effect of Centrifugal Force upon Eggs of Chrysomelid Beetles.f 

 R. W. Hegner has made some interesting experiments yielding the fol- 

 lowing results. 1. Eggs of Chrysomelid beetles, when oriented in a cen- 

 trifugal machine, with either posterior or anterior ends toward the axis 

 of rotation, and subjected to 1500-2000 revolutions per minute for from 

 1 to 12 hours, become stratified into three layers : (a) a light vesicular 

 zone at the inner end, (&) a heavy granular grey cap at the outer end, 

 and (c) a comparatively large intermediate mass of yolk, the larger 

 globules lying at the outer end of this layer. 2. The grey cap is induced 

 by a lesser amount of centrifugal force in an egg containing many cleav- 

 age nuclei than in a fresh egg. Either the grey-cap material is liberated 

 during development, or else some condition of the yolk-mass in the older 

 egg allows it to pass more rapidly toward the heavier end. The grey- 

 cap material is not necessary for the normal development of the embryo. 

 3. The vesicular zone becomes visible after 15 minutes of centrifuging. 

 It is composed of fat imbedded in cytoplasm. This zoue disappears 

 during development. 4. The yolk-globules are distributed through- 

 out the intermediate region of the egg ; the largest spheres are at the 

 outer heavy end. It takes very little centrifugal force to cause this re- 

 arrangement. Restitution to the normal condition takes place soon after 

 the egg is removed from the centrifugal machine. 5. The cytoplasm is 

 lighter than the grey-cap material or the yolk, but heavier than the fat 

 of the vesicular zone. The passage of the cytoplasm to the light end of 

 the egg does not incapacitate it for the production of an embryo. 6. The 

 nuclei are apparently equal in specific gravity to the cytoplasm. Cleavage 

 nuclei and vitellophags rise to the inner end of the egg ; the nuclei of 

 the blastoderm of older eggs are not visibly influenced by centrifugal 

 force. 7. The germ-cell determinations move en masse from their usual 

 position at the posterior end towards the anterior end when the former 

 is placed inward. The further history of these granules has not been 



* Bull. Intemat. Acad. Sci. Cracovie, 1910, pp. 12-16. 

 t Journ. Exper. Zool., vi. (1909) pp. 507-52 (24 figs.). 



