1(32 SUMMARY OF CURRENT RESEARCHES RELATING TO 



A study of the regional occurrence of mitosis and amitosis reveals the 

 fact that the former is found mainly in slowly and the latter in rapidly 

 growing parts of the blastoderm. The idea that the cells which divide 

 by amitosis are on the road to degeneration receives no support from 

 the facts here recorded. Amitosis is probably the result of special 

 physiological conditions which create a stimulus to cell-division, but 

 what these conditions are we are unable to say. 



Post-embryonic Development of Ardeidse.* — S. Schaub has studied 

 Ardea purpurea, A. cinerea and Nyctieorax griseus, with special reference 

 to the changes in the proportions of the body during post-embryonic 

 development, the changes in the scales of the feet, and the distribution 

 of the feathers. He discusses the pterylography in its developmental 

 and phyletic aspects. Emphasis is laid on the primary geometrically 

 precise disposition of the feathers, which is interpreted in con-elation 

 with the strains on the skin. There may have been a primitive diffuse- 

 ness of distribution from which the geometrically orderly arrangements 

 have evolved, but a secondary diffuseness may arise in the definite 

 plumage. Powder-down feathers are peculiarly specialised down-feathers 

 forming a dust whose function seems to be analogous to that of the 

 preen gland. There is no fat about the powder : the greasy feeling is 

 due to the mechanical nature of very flexible minute horny plates. The 

 powder is formed by the degeneration of a cellular sheath around the 

 barbs. But the powder-down feathers of different birds are very diverse, 

 and are rather analogous than homologous structures. 



Complementary Spiracles in Anura.f — P. Wintrebert has corrobo- 

 rated in Alytes obstetricans and Rana temporaria the observation of 

 H. Brauss (on Bombinator) that the opening from the branchial chamber 

 at the beginning of the metamorphosis occurs even in the absence of 

 the anterior limbs. He does not regard this as an " ontogenetic remi- 

 niscence," but gives an ingenious interpretation of the growth-conditions 

 which lead to the perforation. 



Development of Lymph-sacs in Hind Limb of Frog.J— Gizela 

 Goldfinger has studied this on the developing and regenerating limb, 

 and finds that lymph-capillaries ramify, form a network, and coalesce 

 with obliteration of their walls, so that sacs result — a confirmation of 

 Kanvier's view. 



Gastrulation in Teleosteans.§ — J. Boeke maintains that in Teleos- 

 teans (muraenoids) the process of gastrulation is ended as soon as the 

 prostomial thickening has been formed, viz. at the beginning of the 

 covering of the yolk. At that moment the " Anlage " of the entoderm 

 is clearly differentiated, and the ectodermal cells begin to invaginate to 

 form the chorda and mesodermic plates ; the concentration of the cells 

 towards the median line begins ; the long and slender embryo is formed 

 out of the broad and short embryonic shield. The blastula cavity, in 



* Zool. Jahrb., xxv. (1907) pp. 305-404 (2 pis. and 18 figs.). 



t C.R. Soc. Biol. Paris, lxiii. (1907) pp. 439-41. 



% Bull. Acad. Sci. Cracovie, No. 4 (1907) pp. 259-76 (1 pi.). 



§ Proc. Acad. Amsterdam, Section of Sciences, ix. (1907) pp. 800-8 (2 pis.). 



