560 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



surface of the shell-membrane in the egg of the hen. The epithelial 

 cells lie between the shell-membrane and the albumen, require a very- 

 high power for their demonstration, and do not form a continuous layer, 

 but are present sometimes singly, sometimes in groups. The author is 

 of opinion that the cells represent the remnants of the follicular epithe- 

 lium, the whole egg being the follicle. The albumen of the egg must 

 be supposed to have filtered through ihe egg-envelopes. 



Sex of Extra-uterine Foetus.* — Prof. A. Eauber gives a list (made 

 by his assistant, P. Jurjan) of twelve cases of extra-uterine pregnancy, 

 in which the sex distribution was eight males to four females. From this 

 a hasty judgment might infer that the unfavourable nutritive conditions 

 led to a preponderance of males. But in another list which Eauber 

 recently published, there were in eight cases two males and six females. 

 So that the total result shows equality in the occurrence of the two 

 sexes. In man, the author thinks that the evidence points to an ovarian 

 determination of sex. 



Artificial Parthenogenesis in Amphibia and Fishes.t — E. Bataillon 

 has experimented with the eggs of Bana esculenta and various fresh- 

 water fishes. He finds that various solutions provoke segmentation, but 

 he thinks that this is due to a relative dehydration. The influence 

 seems to be physical rather than chemical ; thus the serum of a 

 mammal, both anti-diphtheritic and normal, acts like an isotonic saline 

 or saccharine solution. The influence is one of osmotic pressure. 



Placenta of Macacus.} — |Prof. J. Kollmann finds that in Macacus 

 the development of the placenta is more easily followed than in other 

 mammals. He finds that the mesodermal cone of the villus consists of a 

 double epithelial layer, an outer covering layer, and a deeper layer 

 (Langhans' cells). Both layers originate from the primary ectoderm 

 of the blastodermic vesicle, and neither the cells of the decidua nor the 

 uterine glands take any part in their formation. Neither in Macacus nor 

 in Homo do the chorionic villi possess an endothelial membrane. The 

 spaces between the villi are in the earliest stages a part of the uterine 

 cavity. Until the sixth week they do not normally contain blood. 

 They are extravascular, and the maternal blood bathes directly the 

 embryonic villi. 



Origin and Development of Carotid Grland.§ — Dr. A. Kohn coucludes 

 that the structure found in mammals in the vicinity of the carotid artery 

 is not a gland, nor a network of vessels, but is an organ of peculiar 

 character belonging to the sympathetic system. Its special elements, 

 which he calls chromaffine cells on account of their colour re- 

 actions, its nerve-fibres and ganglion-cells, all originate from the 

 sympathetic, the chromaffine cells arising directly from the cells of the 

 embryonic sympathetic. The organ is best called the paraganglion 

 intercaroticum, and such paraganglia occur in various regions in con- 

 nection with sympathetic ganglia. According to the author, the medulla 

 of the adrenal body is to be reckoned among these paraganglia. In 



* Anat. Anzeig., xvii. (1900) pp. 455-7. 



t Comptes Rendus, cxxxi. (1900) pp. 115-8. 



t Anat. Anzeig., xvii. (1900) pp. 4tf5-79 (6 figs.). 



§ Arch. Mikr. Anat., lvi. (1900) pp. 81-148 (2 pis.). 



