442 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ovarian activity during pregnancy. Ripening of follicles does occur, 

 but it is retarded, and only a few reach full ripeness. On the other hand, 

 the internal secretory function not only continues, but is intensified. 



Spermatozoa entering a Blastula.* — J. H. F. Kohlbrugge has 

 pointed out that in the bat the spermatozoa may penetrate not only into 

 the cells of the uterine mucosa, but may enter the " blastula " and the 

 embryonic disk. In this way the male may have, he suggests, an in- 

 fluence on the embryo apart from amphimixis ; but more facts are required 

 before any speculation of this sort can be entertained. 



Development of Blood.| — A. Maximow has studied this in embryos 

 of rabbit, guinea-pig, cat, and other Mammals. The first blood-cells, 

 arising in blood-islands and lying within vessels, are rounded, indifferent, 

 mesoblast or mesenchyme cells, without haemoglobin. They multiply 

 by independent proliferation and also by continued segregation of en- 

 dothelial cells in the primary vessels. From the outset many become 

 primitive erythroblasts, which multiply independently, but gradually die 

 out. The other primitive blood-cells remain without haemoglobin, and 

 take on the character of non-granular leucocytes or lymphocytes. From 

 some of the progeny of these lymphocytes there arise the definitive red 

 blood corpuscles — first erythroblasts and then erythrocytes. This goes 

 on throughout life, in all places or organs where there are indifferent 

 mesenchymatous migratory cells. The erythroblasts may also proliferate 

 on their own account. Thus red blood corpuscles and white blood cor- 

 puscles arise in the same place and form the same cell-stock — the primi- 

 tive blood-cells in the vessels of the area vasculosa. 



Role of Nucleus in Heredity 4 — Oscar Hertwig returns to the defence 

 of the hypothesis, which Strasburger and he stated in 1884, that the 

 idioplasm is localised in the nuclear substances. In support of this 

 much-discussed thesis he advances seven arguments, of which the three 

 strongest are (1) the equivalence of ovum and spermatozoon as regards 

 nuclear material ; (2) the precise partition of nuclear substance in karyo- 

 kinesis ; and (3) the reduction processes by which an accumulation of 

 nuclear substance is obviated. 



Segmentation of Unfertilised Egg of Fowl.§ — A. Lecaillon continues 

 his study of this phenomenon. If the laid egg be left to itself the blasto- 

 meres which have been formed degenerate and the nuclear figures dis- 

 appear. At the end of an hour there may be only one to be seen. In 

 four days the nuclei have gone. If the temperature be raised the 

 degeneration sets in with great rapidity. 



Early Stages in Development of Rat.|| — Victor Widakowich de- 

 scribes the formation of the " ovum-cylinder," the mesoderm, and the 

 amnion, and discusses the characteristic inversion of the embryo from a 

 dorsally concave to a dorsally convex state. 



* Arch. Mikr. Anat., lxxv. (1910) pp. 519-21 (1 fig.), 

 t Op. cit., lxxiii. (1909) pp. 444-561 (4 pis.). 



% Der Kainpf um Kernfragen der Entwicklungs- und Vererbungslehere. Jena, 

 (1909) 122 pp. $ C.B. Soc. Biol. Paris, lxviii. (1910) pp. 593-4. 



|| Zeitschr. wiss. Zool., sciv. (1909) pp. 240-98 (3 pis. and 1 fig.). 



