THEIR LIFE AND AFFINITY. 247 



One thing, however, we know with certainty, namely, that the human 

 body, hke that of other animals, has its origin in the egg. But the egg 

 itself must be considered as the original animal, as the infusorial crea- 

 ture, appearing in the globular or primary form of animal life, and, like 

 the seed of the plant, containing ideally within itself the whole ani- 

 mal, which, under given external circumstances, it develops really out 

 of itself. Recent observations have shown that the first rudiment of 

 the embryo is formed on the inner surface of the hollow globe of the 

 egg, by folding or turning inwardly a part of the integuments of the 

 egg ; which reminds us distinctly of the purely vegetative bladder-worm 

 (Cysticercus, see p. 244), in which the so-called head, or the absorbing 

 orifice, is turned inwards. It is plain therefore that we must consider 

 the egg in this first period of development also as a plant with a root 

 turned inwards (see p. 243) ; and we find this moreover confirmed by 

 the functionary attributes of its parts, since the first introversion of the 

 integument forms the cavity of the stomach and the intestines, as the first 

 rudiment of the embryo. On the other hand, the external covering of 

 the egg being somewhat similar to the green (breathing) surface of the 

 plant, performs the breathing function of the embrji^o, and contains also 

 (as the latest observations of Pander have shown), in the external envelop 

 of the cuticle, the origin of the organs of sensation. In a further stage of 

 development we see the activity of formation concentrating itself more 

 in the point turned uiwards, and thus producing new opposites. The 

 rudiment of the embryo repeats the above-described form, and the higher 

 animal organs, which commence with the spinal marrow and the vertebral 

 column, originate above the germ of the intestines of the cavity of the 

 stomach. It is now in particular plainly seen how the animal is as it 

 were transformed from a plant into an animal in the maimer above de- 

 scribed (p. 234). For at the very first the intestines are only attached to 

 the foetus, that is, the gut lies as yet in the umbilical cord, just as at first 

 the root is attached to and not in the plant ; but the intestines are soon 

 afterwards drawn more and more inwards, and by degrees are completely 

 enveloped by the animal organs, which grow simultaneously forwards 

 on both sides out of the vertebral column ; and here for the first time 

 the foetus presents the appearance of an independent animal organism. 

 The vascular system, however, is much more slow in connecting itself 

 perfectly with the foetus ; since it is rather a general connecting me- 

 dium in the vegetative sphere, and therefore performs the function of 

 a bond of union between the integument of the egg and llie foetus so 

 long as it remains inclosed in the egg. Even at this period of deve- 

 lopment the relation of the parts of the egg reminds us of the plant ; 

 as the foetus, by means of the umbilical cord, is united to the placenta 

 and integuments of the egg, hold in organic connexion with the ma- 

 ternal organism, just as the flower (which it resembles in respect to the 



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