ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 383 



with the production of a network or granular precipitate. Injury is 

 accompanied by a swelling and an apparent increase in the acid reaction 

 of the part involved. 



The comparatively rigid ectoplasm and the fluid endoplasm of 

 Protozoa are directly comparable to the surface layer and the internal 

 cytoplasm of the marine ova studied. The surface layer and the internal 

 cytoplasm showed themselves equally permeable to the basic vital dyes 

 used. 



The germinal vesicle of an immature egg consists of a hyaline 

 liquid enclosed in a gel-like membrane. The nucleolus is an immiscible 

 droplet floating in the vesicle, and is very sensitive to mechanical injury. 

 The contents of the germinal vesicle of a young ovum have a destructive 

 effect on the cytoplasm. The cytoplasm of an immature egg is much 

 less affected by tearing than is that of the mature egg. In the mature 

 egg the nucleus behaves as a fluid droplet immiscible with the cytoplasm. 

 It may be divided into two droplets, which unite on touching. It 

 readily coagulates if mechanically injured. 



Minute Structure of Nerve-Fibre of Fishes.*— Manuel Sanchez y 

 Sanchez describes the elaborate trabecular and glomerular structures 

 which form a supporting apparatus in the nerve-fibres. 



Oxygen Pressure and Tissue Cultures.f — Montrose T. Burrows has 

 experimented with parts of chick embryos. He finds that they grow in 

 cultures somewhat better in spring and summer than in winter. It 

 seems that cells may grow in an atmosphere of pure oxygen, but their 

 growth, although often slightly more rapid, is not greater in pure 

 oxygen than in a partial pressure of oxygen no more than 9 or 

 10 p.c. The growth becomes less when the partial pressure of oxygen 

 is lower than 9 or 10 p.c, but very evident growth activity is seen in 

 an atmosphere where the partial pressure of the oxygen is as low as 

 45- 6 mm. Hg. The general results show that the activity of the cells 

 in the cultures is little influenced by changes in the oxygen concentra- 

 tion or partial pressure when that remains above a certain amount. 



Structure of Penis in Hedgehog.J — Ed. Retterer and H. Neuville 

 give a detailed account of the minute structure of this organ. Eeaching 

 the glans, the corpora cavernosa and the corpora spongiosa form a 

 median and superior languette at the end of which the urethra opens. 

 The rest of the glans is due to a swelling and vascularization of the 

 fascia penis and of the cutaneous investment. There are voluminous 

 venous plexuses. A thick and long frenum binds the inferior surface of 

 the l)ase of the glans to the prepuce. The urethral epithelium is 

 stratified and pavement-Uke, but when heat sets it it tends to become 

 stratified and cylindrical. 



* Bull. Soc. Espaf). Hist. Nat., xvi. (1916) pp. 467-70 (2 figs.). 

 t Amer. Journ. Physiol., xliii. (1917) pp. 13-21. 

 X C.R. Soc. Biol. Paris, Ixxx. (1917) pp. 83-6. 



