5. Entwicklungslehre. 291 



which contains the germ cell determinants, is killed with a hot needle and 

 these granules are thus prevented from taking part in embryonic development, 

 the embryo produced by the rest of the egg lacks the germ cells. This Sup- 

 plements former experiments in removing the germ cell determinants, and 

 indicates that these granules really determine the germ cells. 



„When the primordial germ cells of Leptinotarsa decemlineata are 

 killed in the blastoderm stage the resulting embryos lack germ cells. This 

 is the earliest known stage in which surgical castration has been performed 

 among the Insecta. 



When the anterior or posterior parts of freshly laid eggs are killed, the 

 material remaining alive develops that part of the embryo which it would 

 have produced if the eggs had remained intact. No regeneration of the 

 part which would have been produced by the killed region takes place. 



If the anterior or posterior parts of eggs in the blastoderm stage (Fig. 2) 

 are killed, the resulting tissue represents the parts of the embryos which 

 would have been produced by the living material if the entire egg had been 

 allowed to develop. 



When parts of young embryos are killed, the remaining tissue develops 

 normally. Even small pieces of tissue, which are widely separated from the 

 rest of the embryo, continue to develop normally. 



Parts of old embryos develop up to the time of hatching. There is no 

 regeneration of the killed part by the living tissue. 



The eggs of Leptinotarsa decemlineata, at the time of deposition 

 are definitely oriented with respect to the future position of the embryo. 

 The areas of the peripheral layer of cytoplasm are already set aside for the 

 production of particular parts of the embryo, and if these areas are killed, the 

 parts of the embryo to which they were destined to give rise will not appear. 

 Likewise areas of the blastoderm are destined to produce certain particular 

 parts of the embryo. Lillie (Chicago). - 



801) Scott, J. W., Further Experiments on the Methods of Egg- 

 Laying in Amphitrite. 



(Biol. Bull. 20,5. p. 252—265. Two figures. April 1911.) 

 The eggs pass out through certain nephridia that are highly modified as 

 gonaducts; only ripe eggs are deposited at recurring periods that bear a close 

 relation to the time of the spring tides. At the time of depositing the eggs 

 the coelomic fluid contains also immature eggs of various sizes, as well as 

 coelomic corpuscles. How are the ripe eggs separated from the other coelomic 

 bodies in the act of oviposition? 



Measurements made on the various bodies suspended in the coelomic fluid 

 show that the eggs increase in specific gravity during growth in the coelome, 

 but that the specific gravity of the corpuscles is decidedly greater than that 

 of the eggs. Studies on the direct action of the cilia of the funnels of the 

 nephridial pouches show that they reject corpuscles and immature eggs while 

 passing the ripe eggs on into the pouches. The author attributes the sifting 

 process to the shape and arrangement of the grooves of the fimbriated mem- 

 brane of the funnel, and especially to the greater plasticity and density of 

 the mature eggs. The funnel is a very delicately adjustecl sifting mechanism. 



Lillie (Chicago). 



802) Cary, L. R., The Formation of Germ-layers in Actinia Ber- 

 mudense. 



(Biol. Bull. 19,6. p. 339—346. 7 figs. 1910.) 



The blastula is filled with a comparatively thin, lightly staining plasma- 



