ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 563 



re<3:ions transplanted to the region approximated by the optic vesicles 

 would give rise to a lens. Werber has shown that numerous isolated 

 lenses may be developed in chemically treated Teleost embryos in the 

 absence of optic vesicles. Spemann and Lewis have shown that the 

 formation of the cornea is a response to stimuli from the optic cup, and 

 will take place even though the lens be removed ; and that the cornea, 

 once formed, degenerates with the removal of the optic cup. Reagan 

 has shown that myocardial concrescence is a tactic response to the 

 presence of endocardial tissue. It is probable that the interaction of 

 parts is of greater importance than is generally recognized. 



Microscopic Study of Reproductive System of Foetal Free- 

 martins.* — Catharine Lines Chapin finds' that those organs in the 

 free-martin which are present in the indifferent stage develop towards 

 the male condition (rete, first set of sex-cords, primary albuginea), and 

 those which develop in the normal female at sex-differentiation or later 

 are inhibited from developing (cords of Pfliiger, definitive albuginea, 

 union of Miillerian ducts to form uterus). The high degree of variation 

 found in the organs of the reproductive system in free-martins is 

 indicative of the variability of the time at which the interstitial 

 secretion of the male embryo may first be introduced into the circulation 

 of the female embryo, and the amount which may be introduced — in 

 other words, the variability of the time and degree of anastomosis of 

 the extra-embryonal blood-vessels of the two embryos. 



The fact that in some free-martins the Wolffian body and Wolffian 

 duct have degenerated more than in a male of corresponding size, 

 though not more than in a female, suggests a later introduction of the 

 secretion of the male, or the introduction of a smaller amount, allowing 

 some development toward the female condition. In one case there was 

 partial union of the horns of the uterus. 



The arrangement of cells in the sex-cords of the free -martin as they 

 are arranged in the seminiferous tubules of the male, and the relatively 

 large size of the sex-cord region, suggest an early introduction of the 

 male influence, made before the beginning or early in the process of 

 degeneration of medullary cords which normally takes place in the 

 female, or the introduction of a sufficiently large amount of male 

 secretion to inhibit female development completely, and to cause 

 development towards the male condition. The development of the 

 Miillerian ducts of a 22*5 cm. free-martin into contorted seminal 

 vesicles of small diameter suggests that the male hormone was intro- 

 duced into the female earlier or in larger amount in this case than in a 

 28 cm. free-martin, in which the Miillerian ducts were still straight 

 ducts of large diameter. 



TheEg-g-cell and its Development.f— A. Brachet has published the 

 substance of a course of lectures on the egg-cell and the factors in 

 development. He empliasizes the transition from embryological study 



* Journ. Exper. Zool., xxiii. (1917) pp. 453-82 (16 figs.). 



t L'CBuf et les Facteurs de I'Ontogenese. A. Brachet. Paris : (1917) 349 pp. 

 (57 figs.). 



