NATURE 



[August 4, 1910 



the "Christian Topograph)'" is the text of two im- 

 portant historical inscriptions which he copied at 

 Adulis, the modern Zulla. One of these was set up 

 by officers of Ptolemy Euergetes, and commemorates 

 that .a^reat king's conquests in the East; the other was 

 added by a local king of the Axumite dynasty, pr<»b- 

 ably in the second century a.d., to chronicle his con- 

 quests in Abyssinia. Historians have to be grateful 

 to the " Christian Topographer " for the preservation 

 of these two documents, and also for the valuable in- 

 formation which he gives us here and there as to the 

 history of his own time. Thus he copied the Adulite 

 inscriptions at the request of Asbas, the Axumite 

 governor, who had been ordered to send copies of 

 them to his master, King Ellatzbaas, who was just 

 then about to set out on his famous expedition to 

 Arabia against Dhu Nuwas, king of Himyar, which 

 was so brilliantly successful. This was about the 

 year 525 k.v>. He gives us also invaluable information 

 as to the great spread of Christianity in the East by 

 the sixth century, especially in Persia and India. 



The book, therefore, was fully worthy of an adequate 

 English edition, and, having made our caveat as to 

 certain blemishes in dealing with the comic side of 

 the subject, we can say that the editor has done his 

 work well, especially, no doubt, upon the textual side. 



TROPHOBLAST AND THE EARLY DEVELOP- 

 MENT OF MAMMALS. 

 Die Saugetierontogenese in Hirer Bedeutung fiir die 



Phylogenie der Wirbeltiere. By Prof. A. A. VV. 



Hubrecht. Pp. V4-247. (Jena: Gustav Fischer, 



1909.) Price 7 marks. 



IT is now twenty years since Prof. Hubrecht pub- 

 lished, in the pages of the Quarterly Journal of 

 Microscopical Science, his classic researches on the 

 trophoblast and allantoic placenta of the hedgehog, 

 Erinaceus europaeus. This work, along with the in- 

 vestigations of Eduard van Beneden and M. Duval, 

 may be said to have revolutionised our knowledge of 

 the placental phenomena in the mammalia. By it 

 new light was thrown on the egg-cleavage, the so- 

 called gastrulation, and, especially, on the mode of 

 origin and the nature of the " foetal membranes," the 

 chorion (trophoblast), amnion, and allantoic placenta. 

 For the Dutch investigator this was the starting-point 

 of a long period of painstaking researches into the 

 placental conditions of diverse mammals, and of these 

 the present work is an author's translation of the 

 English version, published (November, 190S) in the 

 journal containing his earlier results. 



So long ago as 1894, under the title " Spolia 

 nemoris," an appetising account was given of the 

 wonderful array of material of mammalian develop- 

 ment, which, in the Dutch East Indies, had either 

 been collected personally or obtained and sent to 

 Utrecht by others. We do not recall any similar 

 journey in quest of embryological material which 

 has been attended by such remarkable success in en- 

 listing, and retaining, the altruistic help of so many 

 different collectors. Other embryologists remember, 

 to their sorrow, the failure of attempts to increase 

 their collections by the aid of others and amateurs. 

 NO. 2127, VOL. 84] 



This vast material, much of it of rare and interesting 

 species of mammals, has served as the basis of Prof. 

 Hubrecht's researches, and with great generosity he 

 has placed it at the service of other investigators in 

 the Zoological Institute of Utrecht. The limits of 

 space assigned to this notice allow only a general 

 reference to the work before us. 



What is trophoblast ? The word and the thing may 

 be described as the main theme of the work, even 

 though it treats also of the egg-cleavage, germinal 

 layers, allantoic placenta, and the descent of mam- 

 mals. According to Hubrecht, trophoblast is a 

 specialised portion of the outer layer, the epiblast, of 

 the embryo, and he identifies it more particularly as 

 equivalent to that portion of this layer which in 

 amphibians, for example, forms the outer or covering 

 layer. This latter, admittedly, takes no share in the 

 formation of embryonic structures, and it, and tropho- 

 blast also, is regarded by Hubrecht as larval and 

 transitory in character. On the other hand, another 

 mammalian embryologist, Mr. Richard Assheton, has 

 recently again urged the view that trophoblast is in 

 reality a derivative of the inner layer or hypoblast. 

 Apart from other considerations, this identification is, 

 in our opinion, negatived by the circumstance that 

 nowhere in the animal kingdom is the hypoblast 

 known to be formed, as is the trophoblast, as a pro- 

 duct of the first cleavages of the egg. Prof. 

 Hubrecht's own recognition of its embryonic epiblastic 

 nature (that it is really a part of " the embryo ") 

 seems to be disproved by his own researches on 

 Tupaja. Of the eight products of the egg-cleavage 

 here, seven are destined to become trophoblast, while 

 out of the eighth the whole of the embryo, includ- 

 ing presumably its epiblast, is unfolded. If the two 

 foregoing objections be valid, the explanation of the 

 nature of trophoblast must be sought elsewhere, for 

 as yet no one has had the temerity to suggest the 

 remaining alternative, the third germinal layer or 

 mesoblast, as its source of origin. 



The truth is, as so often happens in embryology, far 

 too little account has been taken of physiological con- 

 siderations. The trophoblast arises early in develop- 

 ment, and never takes part in the formation of em- 

 bryonic organs, but instead thereof it eats and erodes 

 its way into the uterine wall, and in doing this it 

 destroys the epithelial lining and much besides. If 

 this happens to be in a tubal (oviducal) gestation, the 

 erosion is finally through the oviduct, with sudden 

 and often fatal haemorrhage into the abdominal cavity. 

 A mass of cells, trophoblast, which can do this, and 

 in the absence of a normal embryo may become 

 the most deadly form of cancer, chorio-epithelioma, 

 can have no nutritive import for the embryo, as its 

 name falsely implies, nor by any stretch of the 

 imagination can it be assigned to either epiblast or 

 hypoblast, for there is nothing in embryology to indi- 

 cate that embr\onic epiblast or hypoblast possesses 

 this property of eroding and destroying maternal 

 tissues. It is not intended as a reproach to the 

 author, or in depreciation of the immense value of his 

 published researches to science, when this lack of in- 

 formation on the physiological and biochemical side is 

 insisted upon. In fine, like so much in embryologv, 



