EMDEN 



are distributed in the course of 

 development in different ways. 

 They happen to have different col- 

 ours, so that they can be followed. 

 There is a yellow peripheral layer 

 which gathers at the lower pole of 

 the egg (where the spermatozoon 

 enters) and there forms a yellow 

 cap. It afterwards moves to form 

 a crescent around the posterior side 

 of the egg just below the equator. 



On the anterior side of the egg 

 there is a grey crescent, at the lower 

 pole between the two crescents 

 there is a slate-blue substance, and 

 at the upper pole there is a zone 

 of colourless living matter. Now, 

 when the egg divides and re- 

 divides the yellow crescent goes 

 into those cells which will become 

 muscle and mesoderm, the grey 

 crescent into cells which become 

 nervous system and the support- 

 ing rod called the notochord, the 

 slate-blue substance into the endo- 

 derm cells lining the future food- 

 canal, and the colourless substance 

 into more ectoderm cells. 



GERMINAL LAYERS. In many 

 developing eggs which are not en- 

 cumbered with much yolk ma- 

 terial, a hollow ball of cells (a bias- 

 tula) becomes in-dimpled or in- 

 vaginated to form a two-layered 

 sac of cells (the gastrula). The 

 outer layer of cells is called the 

 ectoderm or epiblast, the inner 

 layer, the endoderm or hypoblast. 

 The cavity which corresponds to 

 the future digestive cavity is called 

 the archenteron, and the mouth of 

 the sac the blastopore. In sponges 

 and stinging animals there are 

 only two fundamental layers ; in 

 higher forms an intermediate layer, 

 the mesoderm or mesoblast, is 

 established. It is important to 

 notice that these three layers give 

 rise to the same sort of structures 

 throughout the animal kingdom. 



Thus the ectoderm forms the 

 epidermis, the nervous system, and 

 the foundations of the sense- 

 organs. The endoderm forms the 

 lining of the digestive tract and 

 of outgrowths from it. The meso- 

 derm forms muscle and connective 

 tissue, and in many cases (e.g. all 

 vertebrates) the skeleton. It is 

 possible in many cases to go 

 farther back, and point to certain 

 particular cells in the segmented 

 ovum which will form certain 

 structures in the adult, and no 

 others. An early localisation of 

 organ-forming substance is often 

 demonstrable, and it is a remark- 

 able fact that an artificial dis- 

 arrangement of the cells may be 

 put right again by regulation 

 processes which are very charac- 

 teristic of development 



DIFFERENTIATION. As develop- 

 ment proceeds new kinds of ma- 



2886 



terial become evident ; all sorts 

 of different cells nervous, mus- 

 cular, glandular, connective, and 

 so on appear ; tissues and organs 

 arise. In a word, there is a 

 mysterious process of differentia- 

 tion. There is interaction be- 

 tween nuclear substance and cell- 

 substance, there are movements 

 and localisations of different kinds 

 of building material, there are 

 differential (i.e. dissimilar) divi- 

 sions of the cell-substance into 

 heterogeneous daughter-cells which 

 are in some measure partitioned 

 from one another. Thus, to use a 

 metaphor, the developing embryo 

 becomes like a garden in which 

 different plots have come to have 

 different kinds of soil, as well as 

 different relations to one another 

 and to the outer world. A similar 

 handful of seeds, including a score 

 of different kinds (corresponding 

 to the nuclear material), is sown in 

 each plot, but while each plot gets 

 the same kind of seeds, those able 

 to develop in each are different. 



But while differentiation is in pro- 

 gress the developing body is also in- 



EMDEN 



Bibliography. Human Embry- 

 ology, C. S. Minot, repr. 1897 ; The 

 Cell in Development and Inherit- 

 ance, E. B. Wilson, 2nd ed. 1900 ; 

 The Science and Philosophy of the 

 Organism, H. Driesch, 1908 ; Ex- 

 perimental Embryology, J. W. 

 Jenkinson, 1909; Textbook of Em- 

 bryology, ed. W. Heape, 1914, etc. ; 

 Heredity and Environment in the 

 Development of Man, E. G. Conklin, 

 2nd ed. 1916. 



Emden. Seaport and town of 

 Germany. In the Prussian province 

 of Hanover, it stands near the 

 mouth of the Ems, 50 m. W.N. W. of 

 Oldenburg, and is the terminus of 

 the Dortmund-Ems canal. The 

 port and its harbours are on a 

 ship canal, which connects with 

 the Ems, 2| m. away, and other 

 canals passing through the town. 

 The chief ecclesiastical buildings 

 are the Great Church, the Gasthaus 

 Church, and the New Church. The 

 Renaissance town hall, built in the 

 16th century, contains a valuable 

 collection of firearms, and there are 

 museums, colleges, schools, etc. 

 Emden has a large shipping trade, 

 and is an important fishing centre. 



Emden. View of the inner harbour on the canal connecting the town 

 with the river Ems 



tegrated. That is to say, it becomes 

 more and more of a unity, and 

 nothing is more remarkable than 

 the way in which different parts 

 work into one another's hands, and 

 conspire, as it were, towards a co- 

 operative result. The germ is what 

 it is because it has somehow had 

 enregistered within it the many 

 developments manifested in the 

 past by the race to which it belongs. 

 Development is the actualisation 

 of this inheritance, and it comes 

 about in such a way that there is in 

 the individual, especially in the 

 making of organs, a condensed 

 recapitulation of the evolution 

 which has been the work of ages. 



In a general way the develop- 

 ing organism climbs up its own 

 genealogical tree. It must further 

 be noted that the development 

 of the inherited nature always re- 

 quires at least a minimum of ap- 

 propriate nurture if it is to develop 

 aright, and that the fullness of the 

 development depends in some mea- 

 sure on the fullness of the nurture 

 supplied. In this fact, as well as 

 in the slow improvement of the 

 breed, there is hope for mankind. 



Shipbuilding is carried on. Origi- 

 nally a town in East Friesland, in 

 1595 it became a free city under the 

 sovereignty of the Dutch Republic, 

 and in 1744 it was handed over to 

 Prussia. In 1815 it was transferred 

 to Hanover, passing with that 

 kingdom to Prussia in 1866. Pon. 

 24,000. 



Emden. German light cruiser. 

 A sister ship to the Dresden, she 

 displaced 3,600 tons and had ten 

 4'1-in. guns. She was launched in 

 1908. During the Great War 

 the Emden did much damage to 

 British and Allied commerce. 

 Von Miiller, her commander, 

 showed humanity by providing for 

 the safety of the crews of the 

 vessels he sank. While convoying 

 Australian troops to England, the 

 Australian cruiser Sydney learned 

 that the Emden was at Cocos 

 Island and drove her ashore at 

 North Keeling Island and de- 

 stroyed her, Nov. 9, 1914, with 

 the loss of 230 of her crew. Miiller, 

 who was allowed to retain his 

 sword, was among those saved. 

 This was the first actual fighting 

 done by any ship of the Australian 



