160 SUMMARY OF CURRENT RESEARCHES RELATING TO 



or adult, contain only one ovum, the question naturally arises, how do 

 the pluri-ovular follicles originate ? Kosner's sections suggest the answer, 

 that several follicles fuse within the ovary. The whole process may now 

 be summed up, — several primordial follicles fuse, a pluri-ovular follicle 

 results, each of the contained ova is normally fertilised,- each develops 

 with a chorion of its own, but within the investment of the caduca the 

 chorionic partitions are dissolved till only one chorion is left surround- 

 ing all the foetuses, in this case usually four in number. That the 

 monochorial foetuses should always be of the same sex is interpretable 

 as due to the similarity of environing conditions, from the Graafian 

 follicle onwards. 



If the evidence from armadillo to man be admitted as cogent, we 

 may venture to conclude that monochorial human twins start from a 

 bi-ovular Graafian follicle, whose two ova, normally fertilised, find lodg- 

 ment within one caduca-investment and develop within one chorion 

 formed from the fusion of two. 



Origin of Blood-Vessels.* — Prof. E. S. Bergh outlines a theory as 

 to the phylogenetic origin of the blood-vessels from a foundation of con- 

 tractile cells. The full argument is promised at an early date. 



A study of the vascular system of Vertebrates leads one to give 

 prominence to the internal epithelium (so-called endothelium), which is 

 present in all the blood-vessels and in the heart, is the sole component 

 of the capillaries, and appears in development before other parts of the 

 vessels. Is it the Urgewebe ? A negative answer is suggested by a 

 study of Invertebrates, where endothelium in the main vessels is con- 

 spicuous by its absence. Only in the small vessels is a true internal 

 epithelium demonstrable. 



Bergh supposes that canals were formed in the primitive body-cavity 

 with contractile walls, that the contractility became afterwards localised 

 to definite regions of the canal system, and that in the parts where con- 

 tractile elements disappeared a new tissue — the endothelium — was differ- 

 entiated, especially where active exchange of substances between the 

 blood and the tissues occurred. This endothelium — regulating exchange 

 — was at first perfected peripherally, and its centripetal extension was 

 secondary. 



Influences of Injections into the Albumen of Fowls' Eggs, f — 

 Prof. W. Schimkewitsch gives a preliminary account of the strange 

 changes induced by injecting solutions of sugar, salt, &c, into the 

 albumen of the developing egg of the hen. The list includes blasto- 

 dermic discs which show a syncytium of cells and yolk-spherules, unequal 

 growth, imperfect development, complete inhibition of development, de- 

 formations, dwarfings, local enlargements, asymmetry, and so on. But 

 we must await the more detailed description with figures and interpre- 

 tations which the author promises to publish shortly. 



Cell-division and Mitosis.J — Prof. M. Nussbaum discusses some of the 

 debated points connected with the division of cells and of nuclei, giving 

 an account of his own observations on the segmentation of living and 



* Anat. Anzeig., xx. (1902) pp. 488-92. f Tom. cit. pp. 507-10. 



t Arch. Mikr. Anat., lix. (1902) pp. 647-84 (2 pis. and 1 fig.). 



